PHP FAQ
MYSQL Tricks
PHP MYSQL INTERVIEW
PHP TIPS & Tricks
PHP Interview Questions, Answers [Php FAQ ]
What are the popular frameworks in PHP? Some popular PHP frameworks are:
CodeIgniter
CakePHP
Symfony
Zend Framewor Yii 2
Name the popular Content Management Systems (CMS) in PHP.
WordPress
Joomla
Magento
Drupal
What's PHP ?
The PHP Hypertext Preprocessor is a programming language that allows web developers
to create dynamic content that interacts with databases. PHP is basically used
for developing web based software applications.
What Is a Session?
A session is a logical object created by the PHP engine to allow you to preserve
data across subsequent HTTP requests.
There is only one session object available to your PHP scripts at any time.
Data saved to the session by a script can be retrieved by the same script or
another script when requested from the same visitor.
Sessions are commonly used to store temporary data to allow multiple PHP pages to offer a complete functional transaction for the same visitor.
What is meant by PEAR in php?
Answer1:
PEAR is the next revolution in PHP. This repository is bringing higher level
programming to PHP. PEAR is a framework and distribution system for reusable
PHP components. It eases installation by bringing an automated wizard, and packing
the strength and experience of PHP users into a nicely organised OOP library.
PEAR also provides a command-line interface that can be used to automatically
install "packages"
Answer2:
PEAR is short for "PHP Extension and Application Repository" and is
pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the governing body.
The project has been founded by Stig S. Bakken in 1999 and quite a lot of people
have joined the project since then.
How can we know the number of days between two given dates using PHP?
Simple arithmetic:
$date1 = date('Y-m-d');
$date2 = '2006-07-01';
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo "Number of days since '2006-07-01': $days";
How can we repair a MySQL table?
The syntex for repairing a mysql table is:
REPAIR TABLE tablename
REPAIR TABLE tablename QUICK
REPAIR TABLE tablename EXTENDED
This command will repair the table specified.
If QUICK is given, MySQL will do a repair of only the index tree.
If EXTENDED is given, it will create index row by row.
What is the difference between $message and $$message?
Anwser 1:
$message is a simple variable whereas $$message is a reference variable. Example:
$user = 'bob'
is equivalent to
$holder = 'user';
$$holder = 'bob';
Anwser 2:
They are both variables. But $message is a variable with a fixed name. $$message
is a variable who's name is stored in $message. For example, if $message contains
"var", $$message is the same as $var.
What Is a Persistent Cookie?
A persistent cookie is a cookie which is stored in a cookie file permanently
on the browser's computer. By default, cookies are created as temporary cookies
which stored only in the browser's memory. When the browser is closed, temporary
cookies will be erased. You should decide when to use temporary cookies and
when to use persistent cookies based on their differences:
*Temporary cookies can not be used for tracking long-term information.
*Persistent cookies can be used for tracking long-term information.
*Temporary cookies are safer because no programs other than the browser can
access them.
*Persistent cookies are less secure because users can open cookie files see
the cookie values.
What does a special set of tags <?= and ?>
do in PHP?
The output is displayed directly to the browser.
How do you define a constant?
Via define() directive, like define ("MYCONSTANT", 100);
What are the differences between require and include,
include_once?
Anwser 1:
require_once() and include_once() are both the functions to include and evaluate
the specified file only once. If the specified file is included previous to
the present call occurrence, it will not be done again.
But require() and include() will do it as many times they are asked to do.
Anwser 2:
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include() statement,
with the only difference being that if the code from a file has already been
included, it will not be included again. The major difference between include()
and require() is that in failure include() produces a warning message whereas
require() produces a fatal errors.
Anwser 3:
All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include()
does not.
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include() statement,
with the only difference being that if the code from a file has already been
included, it will not be included again. It des not call a fatal error if file
not exists. require_once() does the same as include_once(), but it calls a fatal
error if file not exists.
Anwser 4:
File will not be included more than once. If we want to include a file once
only and further calling of the file will be ignored then we have to use the
PHP function include_once(). This will prevent problems with function redefinitions,
variable value reassignments, etc.
What is meant by urlencode and urldecode?
Anwser 1:
urlencode() returns the URL encoded version of the given string. URL coding
converts special characters into % signs followed by two hex digits. For example:
urlencode("10.00%") will return "10%2E00%25". URL encoded
strings are safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.
Anwser 2:
string urlencode(str) - Returns the URL encoded version of the input string.
String values to be used in URL query string need to be URL encoded. In the
URL encoded version:
Alphanumeric characters are maintained as is.
Space characters are converted to "+" characters.
Other non-alphanumeric characters are converted "%" followed by two
hex digits representing the converted character.
string urldecode(str) - Returns the original string of the input URL encoded
string.
For example:
$discount ="10.00%";
$url = "http://domain.com/submit.php?disc=".urlencode($discount);
echo $url;
You will get "http://domain.com/submit.php?disc=10%2E00%25".
How To Get the Uploaded File Information in the
Receiving Script?
Once the Web server received the uploaded file, it will call the PHP script
specified in the form action attribute to process them. This receiving PHP script
can get the uploaded file information through the predefined array called $_FILES.
Uploaded file information is organized in $_FILES as a two-dimensional array
as:
$_FILES[$fieldName]['name'] - The Original file name on the browser system.
$_FILES[$fieldName]['type'] - The file type determined by the browser.
$_FILES[$fieldName]['size'] - The Number of bytes of the file content.
$_FILES[$fieldName]['tmp_name'] - The temporary filename of the file in which
the uploaded file was stored on the server.
$_FILES[$fieldName]['error'] - The error code associated with this file upload.
The $fieldName is the name used in the <INPUT TYPE=FILE, NAME=fieldName>.
What is the difference between mysql_fetch_object
and mysql_fetch_array?
MySQL fetch object will collect first single matching record where mysql_fetch_array
will collect all matching records from the table in an array
How can I execute a PHP script using command line?
Just run the PHP CLI (Command Line Interface) program and provide the PHP script
file name as the command line argument. For example, "php myScript.php",
assuming "php" is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may
not execute properly in command line environment.
I am trying to assign a variable the value of 0123, but it keeps coming up with
a different number, what’s the problem?
PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar
PHP interview questions for more numeric problems.
Would I use print "$a dollars" or "{$a}
dollars" to print out the amount of dollars in this example?
In this example it wouldn’t matter, since the variable is all by itself,
but if you were to print something like "{$a},000,000 mln dollars",
then you definitely need to use the braces.
What are the different tables present in MySQL?
Which type of table is generated when we are creating a table in the following
syntax: create table employee(eno int(2),ename varchar(10))?
Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23. When you fire the above
create query MySQL will create a MyISAM table.
How To Create a Table?
If you want to create a table, you can run the CREATE TABLE statement as shown
in the following sample script:
<?php
include "mysql_connection.php";
$sql = "CREATE TABLE Tech_links ("
. " id INTEGER NOT NULL"
. ", url VARCHAR(80) NOT NULL"
. ", notes VARCHAR(1024)"
. ", counts INTEGER"
. ", time TIMESTAMP DEFAULT sysdate()"
. ")";
if (mysql_query($sql, $con)) {
print("Table Tech_links created.\n");
} else {
print("Table creation failed.\n");
}
mysql_close($con);
?>
Remember that mysql_query() returns TRUE/FALSE on CREATE statements. If you
run this script, you will get something like this:
Table Tech_links created.
How can we encrypt the username and password using
PHP?
Answer1
You can encrypt a password with the following Mysql>SET PASSWORD=PASSWORD("Password");
Answer2
You can use the MySQL PASSWORD() function to encrypt username and password.
For example,
INSERT into user (password, ...) VALUES (PASSWORD($password”)), ...);
How do you pass a variable by value?
Just like in C++, put an ampersand in front of it, like $a = &$b
What is the functionality of the functions STRSTR()
and STRISTR()?
string strstr ( string haystack, string needle ) returns part of haystack string
from the first occurrence of needle to the end of haystack. This function is
case-sensitive.
stristr() is idential to strstr() except that it is case insensitive.
When are you supposed to use endif to end the
conditional statement?
When the original if was followed by : and then the code block without braces.
How can we send mail using JavaScript?
No. There is no way to send emails directly using JavaScript.
But you can use JavaScript to execute a client side email program send the
email using the "mailto" code. Here is an example:
function myfunction(form)
{
tdata=document.myform.tbox1.value;
location="mailto:mailid@domain.com?subject=...";
return true;
}
What is the functionality of the function strstr
and stristr?
strstr() returns part of a given string from the first occurrence of a given
substring to the end of the string. For example: strstr("user@example.com","@")
will return "@example.com".
stristr() is idential to strstr() except that it is case insensitive.
What is the difference between ereg_replace()
and eregi_replace()?
eregi_replace() function is identical to ereg_replace() except that it ignores
case distinction when matching alphabetic characters.
How do I find out the number of parameters passed into function9. ?
func_num_args() function returns the number of parameters passed in.
What is the purpose of the following files having
extensions: frm, myd, and myi? What these files contain?
In MySQL, the default table type is MyISAM.
Each MyISAM table is stored on disk in three files. The files have names that
begin with the table name and have an extension to indicate the file type.
The '.frm' file stores the table definition.
The data file has a '.MYD' (MYData) extension.
The index file has a '.MYI' (MYIndex) extension,
If the variable $a is equal to 5 and variable $b is equal to character a, what’s
the value of $$b?
100, it’s a reference to existing variable.
How To Protect Special Characters in Query String?
If you want to include special characters like spaces in the query string, you
need to protect them by applying the urlencode() translation function. The script
below shows how to use urlencode():
<?php
print("<html>");
print("<p>Please click the links below"
." to submit comments about TECHPreparation.com:</p>");
$comment = 'I want to say: "It\'s a good site! :->"';
$comment = urlencode($comment);
print("<p>"
."<a href=\"processing_forms.php?name=Guest&comment=$comment\">"
."It's an excellent site!</a></p>");
$comment = 'This visitor said: "It\'s an average site! :-("';
$comment = urlencode($comment);
print("<p>"
.'<a href="processing_forms.php?'.$comment.'">'
."It's an average site.</a></p>");
print("</html>");
?>
Are objects passed by value or by reference?
Everything is passed by value.
What are the differences between DROP a table
and TRUNCATE a table?
DROP TABLE table_name - This will delete the table and its data.
TRUNCATE TABLE table_name - This will delete the data of the table, but not
the table definition.
How do you call a constructor for a parent class?
parent::constructor($value)
WHAT ARE THE DIFFERENT TYPES OF ERRORS IN PHP?
Here are three basic types of runtime errors in PHP:
1. Notices: These are trivial, non-critical errors that PHP encounters while
executing a script - for example, accessing a variable that has not yet been
defined. By default, such errors are not displayed to the user at all - although
you can change this default behavior.
2. Warnings: These are more serious errors - for example, attempting to include()
a file which does not exist. By default, these errors are displayed to the user,
but they do not result in script termination.
3. Fatal errors: These are critical errors - for example, instantiating an
object of a non-existent class, or calling a non-existent function. These errors
cause the immediate termination of the script, and PHP's default behavior is
to display them to the user when they take place.
Internally, these variations are represented by twelve different error types
What’s the special meaning of __sleep and __wakeup?
__sleep returns the array of all the variables than need to be saved, while
__wakeup retrieves them.
How can we submit a form without a submit button?
If you don't want to use the Submit button to submit a form, you can use normal
hyper links to submit a form. But you need to use some JavaScript code in the
URL of the link. For example:
<a href="javascript: document.myform.submit();">Submit Me</a>
How can we register the variables into a session?
session_register($session_var);
$_SESSION['var'] = 'value';
What is the difference between characters \023 and \x23?
The first one is octal 23, the second is hex 23.
With a heredoc syntax, do I get variable substitution inside the heredoc contents?
Yes.
How can we submit form without a submit button?
We can use a simple JavaScript code linked to an event trigger of any form field.
In the JavaScript code, we can call the document.form.submit() function to submit
the form. For example: <input type=button value="Save" onClick="document.form.submit()">
How can we create a database using PHP and mysql?
We can create MySQL database with the use of mysql_create_db($databaseName)
to create a database.
How many ways we can retrieve the date in result set of mysql using php?
As individual objects so single record or as a set or arrays.
Can we use include ("abc.php") two times
in a php page "makeit.php"?
Yes.
For printing out strings, there are echo, print and printf. Explain the differences.
echo is the most primitive of them, and just outputs the contents following
the construct to the screen. print is also a construct (so parentheses are optional
when calling it), but it returns TRUE on successful output and FALSE if it was
unable to print out the string. However, you can pass multiple parameters to
echo, like:
<?php echo 'Welcome ', 'to', ' ', 'techpreparations!'; ?>
and it will output the string "Welcome to techpreparations!" print
does not take multiple parameters. It is also generally argued that echo is
faster, but usually the speed advantage is negligible, and might not be there
for future versions of PHP. printf is a function, not a construct, and allows
such advantages as formatted output, but it’s the slowest way to print
out data out of echo, print and printf.
I am writing an application in PHP that outputs a printable version of driving
directions. It contains some long sentences, and I am a neat freak, and would
like to make sure that no line exceeds 50 characters. How do I accomplish that
with PHP?
On large strings that need to be formatted according to some length specifications,
use wordwrap() or chunk_split().
What’s the output of the ucwords function in this example?
$formatted = ucwords("TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS");
print $formatted;
What will be printed is TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS.
ucwords() makes every first letter of every word capital, but it does not lower-case
anything else. To avoid this, and get a properly formatted string, it’s
worth using strtolower() first.
What’s the difference between htmlentities() and htmlspecialchars()?
htmlspecialchars only takes care of <, >, single quote ‘, double
quote " and ampersand. htmlentities translates all occurrences of character
sequences that have different meaning in HTML.
How can we extract string "abc.com" from a string "mailto:info@abc.com?subject=Feedback"
using regular expression of PHP?
$text = "mailto:info@abc.com?subject=Feedback";
preg_match('.*@([^?]*)', $text, $output);
echo $output[1];
Note that the second index of $output, $output[1], gives the match, not the
first one, $output[0].
So if md5() generates the most secure hash, why would you ever use the less
secure crc32() and sha1()?
Crypto usage in PHP is simple, but that doesn’t mean it’s free.
First off, depending on the data that you’re encrypting, you might have
reasons to store a 32-bit value in the database instead of the 160-bit value
to save on space. Second, the more secure the crypto is, the longer is the computation
time to deliver the hash value. A high volume site might be significantly slowed
down, if frequent md5() generation is required.
How can we destroy the session, how can we unset the variable of a session?
session_unregister() - Unregister a global variable from the current session
session_unset() - Free all session variables
What are the different functions in sorting an
array?
Sorting functions in PHP:
asort()
arsort()
ksort()
krsort()
uksort()
sort()
natsort()
rsort()
How can we know the count/number of elements of
an array?
2 ways:
a) sizeof($array) - This function is an alias of count()
b) count($urarray) - This function returns the number of elements in an array.
Interestingly if you just pass a simple var instead of an array, count() will
return 1.
How many ways we can pass the variable through
the navigation between the pages?
At least 3 ways:
1. Put the variable into session in the first page, and get it back from session
in the next page.
2. Put the variable into cookie in the first page, and get it back from the
cookie in the next page.
3. Put the variable into a hidden form field, and get it back from the form
in the next page.
What is the maximum length of a table name, a
database name, or a field name in MySQL?
Database name: 64 characters
Table name: 64 characters
Column name: 64 characters
How many values can the SET function of MySQL
take?
MySQL SET function can take zero or more values, but at the maximum it can take
64 values.
What are the other commands to know the structure
of a table using MySQL commands except EXPLAIN command?DESCRIBE table_name;
How can we find the number of rows in a table
using MySQL?
Use this for MySQL
SELECT COUNT(*) FROM table_name;
What’s the difference between md5(), crc32()
and sha1() crypto on PHP?
The major difference is the length of the hash generated. CRC32 is, evidently,
32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value.
This is important when avoiding collisions.
How can we find the number of rows in a result
set using PHP?
Here is how can you find the number of rows in a result set in PHP:
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";
How many ways we can we find the current date
using MySQL?
SELECT CURDATE();
SELECT CURRENT_DATE();
SELECT CURTIME();
SELECT CURRENT_TIME();
Give the syntax of GRANT commands?
The generic syntax for GRANT is as following
GRANT [rights] on [database] TO [username@hostname] IDENTIFIED BY [password]
Now rights can be:
a) ALL privilages
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all databse by usingh *.* or some specific database
by database.* or a specific table by database.table_name.
Give the syntax of REVOKE commands?
The generic syntax for revoke is as following
REVOKE [rights] on [database] FROM [username@hostname]
Now rights can be:
a) ALL privileges
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all database by using *.* or some specific database
by database.* or a specific table by database.table_name.
What is the difference between CHAR and VARCHAR data types?
CHAR is a fixed length data type. CHAR(n) will take n characters of storage
even if you enter less than n characters to that column. For example, "Hello!"
will be stored as "Hello! " in CHAR(10) column.
VARCHAR is a variable length data type. VARCHAR(n) will take only the required
storage for the actual number of characters entered to that column. For example,
"Hello!" will be stored as "Hello!" in VARCHAR(10) column.
How can we encrypt and decrypt a data present in a mysql table using mysql?
AES_ENCRYPT() and AES_DECRYPT()
Will comparison of string "10" and integer
11 work in PHP?
Yes, internally PHP will cast everything to the integer type, so numbers 10
and 11 will be compared.
What is the functionality of MD5 function in PHP?
string md5(string)
It calculates the MD5 hash of a string. The hash is a 32-character hexadecimal
number.
How can I load data from a text file into a table?
The MySQL provides a LOAD DATA INFILE command. You can load data from a file.
Great tool but you need to make sure that:
a) Data must be delimited
b) Data fields must match table columns correctly
How can we know the number of days between two
given dates using MySQL?
Use DATEDIFF()
SELECT DATEDIFF(NOW(),'2006-07-01');
How can we change the name of a column of a table?
This will change the name of column:
ALTER TABLE table_name CHANGE old_colm_name new_colm_name
How can we change the data type of a column of a table?
This will change the data type of a column:
ALTER TABLE table_name CHANGE colm_name same_colm_name [new data type]
What is the difference between GROUP BY and ORDER BY in SQL?
To sort a result, use an ORDER BY clause.
The most general way to satisfy a GROUP BY clause is to scan the whole table
and create a new temporary table where all rows from each group are consecutive,
and then use this temporary table to discover groups and apply aggregate functions
(if any).
ORDER BY [col1],[col2],...[coln]; Tells DBMS according to what columns it should
sort the result. If two rows will have the same value in col1 it will try to
sort them according to col2 and so on.
GROUP BY [col1],[col2],...[coln]; Tells DBMS to group (aggregate) results with
same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with
it, if you want to count all items in group, sum all values or view average.
What is meant by MIME?
Answer 1:
MIME is Multipurpose Internet Mail Extensions is an Internet standard for the
format of e-mail. However browsers also uses MIME standard to transmit files.
MIME has a header which is added to a beginning of the data. When browser sees
such header it shows the data as it would be a file (for example image)
Some examples of MIME types:
audio/x-ms-wmp
image/png
application/x-shockwave-flash
Answer 2:
Multipurpose Internet Mail Extensions.
WWW's ability to recognize and handle files of different types is largely dependent
on the use of the MIME (Multipurpose Internet Mail Extensions) standard. The
standard provides for a system of registration of file types with information
about the applications needed to process them. This information is incorporated
into Web server and browser software, and enables the automatic recognition
and display of registered file types. …
How can we know that a session is started or not?
A session starts by session_start() function.
This session_start() is always declared in header portion. it always declares
first. then we write session_register().
What are the differences between mysql_fetch_array(), mysql_fetch_object(),
mysql_fetch_row()?
Answer 1:
mysql_fetch_array() -> Fetch a result row as a combination of associative
array and regular array.
mysql_fetch_object() -> Fetch a result row as an object.
mysql_fetch_row() -> Fetch a result set as a regular array().
Answer 2:
The difference between mysql_fetch_row() and mysql_fetch_array() is that the
first returns the results in a numeric array ($row[0], $row[1], etc.), while
the latter returns a the results an array containing both numeric and associative
keys ($row['name'], $row['email'], etc.). mysql_fetch_object() returns an object
($row->name, $row->email, etc.).
If we login more than one browser windows at the same time with same user and
after that we close one window, then is the session is exist to other windows
or not? And if yes then why? If no then why?
Session depends on browser. If browser is closed then session is lost. The session
data will be deleted after session time out. If connection is lost and you recreate
connection, then session will continue in the browser.
What are the MySQL database files stored in system
?
Data is stored in name.myd
Table structure is stored in name.frm
Index is stored in name.myi
What is the difference between PHP4 and PHP5?
PHP4 cannot support oops concepts and Zend engine 1 is used.
PHP5 supports oops concepts and Zend engine 2 is used.
Error supporting is increased in PHP5.
XML and SQLLite will is increased in PHP5.
Can we use include(abc.PHP) two times in a PHP
page makeit.PHP”?
Yes we can include that many times we want, but here are some things to make
sure of:
(including abc.PHP, the file names are case-sensitive)
there shouldn't be any duplicate function names, means there should not be functions
or classes or variables with the same name in abc.PHP and makeit.php
What are the differences between mysql_fetch_array(),
mysql_fetch_object(), mysql_fetch_row()?
mysql_fetch_array - Fetch a result row as an associative array and a numeric
array.
mysql_fetch_object - Returns an object with properties that correspond to the
fetched row and moves the internal data pointer ahead. Returns an object with
properties that correspond to the fetched row, or FALSE if there are no more
rows
mysql_fetch_row() - Fetches one row of data from the result associated with
the specified result identifier. The row is returned as an array. Each result
column is stored in an array offset, starting at offset 0.
What is meant by nl2br()?
Anwser1:
nl2br() inserts a HTML tag <br> before all new line characters \n in a
string.
echo nl2br("god bless \n you");
output:
god bless<br>
you
How can we encrypt and decrypt a data presented
in a table using MySQL?
You can use functions: AES_ENCRYPT() and AES_DECRYPT() like:
AES_ENCRYPT(str, key_str)
AES_DECRYPT(crypt_str, key_str)
How can I retrieve values from one database server
and store them in other database server using PHP?
For this purpose, you can first read the data from one server into session variables.
Then connect to other server and simply insert the data into the database.
Who is the father of PHP and what is the current version of PHP and MYSQL?
Rasmus Lerdorf.
PHP 5.1. Beta
MySQL 5.0
In how many ways we can retrieve data in the result set of MYSQL using
PHP?
mysql_fetch_array - Fetch a result row as an associative array, a numeric array,
or both
mysql_fetch_assoc - Fetch a result row as an associative array
mysql_fetch_object - Fetch a result row as an object
mysql_fetch_row —- Get a result row as an enumerated array
What are the functions for IMAP?
imap_body - Read the message body
imap_check - Check current mailbox
imap_delete - Mark a message for deletion from current mailbox
imap_mail - Send an email message
What are encryption functions in PHP?
CRYPT()
MD5()
What is the difference between htmlentities() and htmlspecialchars()?
htmlspecialchars() - Convert some special characters to HTML entities (Only
the most widely used)
htmlentities() - Convert ALL special characters to HTML entities
What is the functionality of the function htmlentities?
htmlentities() - Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except with htmlentities(),
all characters which have HTML character entity equivalents are translated into
these entities.
How can we get the properties (size, type, width,
height) of an image using php image functions?
To know the image size use getimagesize() function
To know the image width use imagesx() function
To know the image height use imagesy() function
How can we increase the execution time of a php script?
By the use of void set_time_limit(int seconds)
Set the number of seconds a script is allowed to run. If this is reached, the
script returns a fatal error. The default limit is 30 seconds or, if it exists,
the max_execution_time value defined in the php.ini. If seconds is set to zero,
no time limit is imposed.
When called, set_time_limit() restarts the timeout counter from zero. In other
words, if the timeout is the default 30 seconds, and 25 seconds into script
execution a call such as set_time_limit(20) is made, the script will run for
a total of 45 seconds before timing out.
HOW CAN WE TAKE A BACKUP OF A MYSQL TABLE AND
HOW CAN WE RESTORE IT?
Answer 1:
Create a full backup of your database: shell> mysqldump tab=/path/to/some/dir
opt db_name
Or: shell> mysqlhotcopy db_name /path/to/some/dir
The full backup file is just a set of SQL statements, so restoring it is very
easy:
shell> mysql "."Executed";
Answer 2:
To backup: BACKUP TABLE tbl_name TO /path/to/backup/directory
’ To restore: RESTORE TABLE tbl_name FROM /path/to/backup/directory
mysqldump: Dumping Table Structure and Data
Utility to dump a database or a collection of database for backup or for transferring
the data to another SQL server (not necessarily a MySQL server). The dump will
contain SQL statements to create the table and/or populate the table.
-t, no-create-info
Don't write table creation information (the CREATE TABLE statement).
-d, no-data
Don't write any row information for the table. This is very useful if you just
want to get a dump of the structure for a table!
How to set cookies?
setcookie('variable','value','time')
;
variable - name of the cookie variable
value - value of the cookie variable
time - expiry time
Example: setcookie('Test',$i,time()+3600);
Test - cookie variable name
$i - value of the variable 'Test'
time()+3600 - denotes that the cookie will expire after an one hour
How to reset/destroy a cookie ?
Reset a cookie by specifying expire time in the past:
Example: setcookie('Test',$i,time()-3600); // already expired time
Reset a cookie by specifying its name only
Example: setcookie('Test');
What types of images that PHP supports ?
Using imagetypes() function to find out what types of images are supported in
your PHP engine.
imagetypes() - Returns the image types supported.
This function returns a bit-field corresponding to the image formats supported
by the version of GD linked into PHP. The following bits are returned, IMG_GIF
IMG_JPG IMG_PNG IMG_WBMP IMG_XPM.
Check if a variable is an integer in JAVASCRIPT ?
var myValue =9.8;
if(parseInt(myValue)== myValue)
alert('Integer');
else
alert('Not an integer');
Tools used for drawing ER diagrams.
Case Studio
Smart Draw
How can I know that a variable is a number or not using
a JavaScript?
Answer 1:
bool is_numeric( mixed var)
Returns TRUE if var is a number or a numeric string, FALSE otherwise.
Answer 2:
Definition and Usage
The isNaN() function is used to check if a value is not a number.
Syntax
isNaN(number)
Parameter Description
number Required. The value to be tested
How can we submit from without a submit button?
Trigger the JavaScript code on any event ( like onSelect of drop down list box,
onfocus, etc ) document.myform.submit(); This will submit the form.
How many ways can we get the value of current session id?
session_id() returns the session id for the current session.
How can we destroy the cookie?
Set the cookie with a past expiration time.
What are the current versions of Apache, PHP, and MySQL?
PHP: PHP 5.1.2
MySQL: MySQL 5.1
Apache: Apache 2.1
What are the reasons for selecting LAMP (Linux,
Apache, MySQL, Php) instead of combination of other software programs, servers
and operating systems?
All of those are open source resource. Security of Linux is very more
than windows. Apache is a better server that IIS both in functionality and security.
Mysql is world most popular open source database. Php is more faster that asp
or any other scripting language.
What are the features and advantages of OBJECT
ORIENTED PROGRAMMING?
One of the main advantages of OO programming is its ease of modification; objects
can easily be modified and added to a system there by reducing maintenance costs.
OO programming is also considered to be better at modeling the real world than
is procedural programming. It allows for more complicated and flexible interactions.
OO systems are also easier for non-technical personnel to understand and easier
for them to participate in the maintenance and enhancement of a system because
it appeals to natural human cognition patterns. For some systems, an OO approach
can speed development time since many objects are standard across systems and
can be reused. Components that manage dates, shipping, shopping carts, etc.
can be purchased and easily modified for a specific system.
How can we get second of the current time using
date function?
$second = date("s");
What is the use of friend function?
Friend functions
Sometimes a function is best shared among a number of different classes. Such
functions can be declared either as member functions of one class or as global
functions. In either case they can be set to be friends of other classes, by
using a friend specifier in the class that is admitting them. Such functions
can use all attributes of the class which names them as a friend, as if they
were themselves members of that class.
A friend declaration is essentially a prototype for a member function, but instead
of requiring an implementation with the name of that class attached by the double
colon syntax, a global function or member function of another class provides
the match.
class mylinkage
{
private:
mylinkage * prev;
mylinkage * next;
protected:
friend void set_prev(mylinkage* L, mylinkage* N);
void set_next(mylinkage* L);
public:
mylinkage * succ();
mylinkage * pred();
mylinkage();
};
void mylinkage::set_next(mylinkage* L) { next = L; }
void set_prev(mylinkage * L, mylinkage * N ) { N->prev = L; }
Friends in other classes
It is possible to specify a member function of another class as a friend as
follows:
class C
{
friend int B::f1();
};
class B
{
int f1();
};
It is also possible to specify all the functions in another class as friends,
by specifying the entire class as a friend.
class A
{
friend class B;
};
Friend functions allow binary operators to be defined which combine private
data in a pair of objects. This is particularly powerful when using the operator
overloading features of C++. We will return to it when we look at overloading.
How can we get second of the current time using date function?
$second = date("s");
What is the maximum size of a file that can be uploaded using PHP and how can
we change this?
You can change maximum size of a file set upload_max_filesize variable in php.ini
file
How can I make a script that can be bilingual
(supports English, German)?
You can change char set variable in above line in the script to support bi language.
What are the difference between abstract class and interface?
Abstract class: abstract classes are the class where one or more methods are
abstract but not necessarily all method has to be abstract. Abstract methods
are the methods, which are declare in its class but not define. The definition
of those methods must be in its extending class.
Interface: Interfaces are one type of class where all the methods are abstract.
That means all the methods only declared but not defined. All the methods must
be define by its implemented class.
What are the advantages of stored procedures,
triggers, indexes?
A stored procedure is a set of SQL commands that can be compiled and stored
in the server. Once this has been done, clients don't need to keep re-issuing
the entire query but can refer to the stored procedure. This provides better
overall performance because the query has to be parsed only once, and less information
needs to be sent between the server and the client. You can also raise the conceptual
level by having libraries of functions in the server. However, stored procedures
of course do increase the load on the database server system, as more of the
work is done on the server side and less on the client (application) side. Triggers
will also be implemented. A trigger is effectively a type of stored procedure,
one that is invoked when a particular event occurs. For example, you can install
a stored procedure that is triggered each time a record is deleted from a transaction
table and that stored procedure automatically deletes the corresponding customer
from a customer table when all his transactions are deleted. Indexes are used
to find rows with specific column values quickly. Without an index, MySQL must
begin with the first row and then read through the entire table to find the
relevant rows. The larger the table, the more this costs. If the table has an
index for the columns in question, MySQL can quickly determine the position
to seek to in the middle of the data file without having to look at all the
data. If a table has 1,000 rows, this is at least 100 times faster than reading
sequentially. If you need to access most of the rows, it is faster to read sequentially,
because this minimizes disk seeks.
What is maximum size of a database in mysql?
If the operating system or filesystem places a limit on the number of files
in a directory, MySQL is bound by that constraint. The efficiency of the operating
system in handling large numbers of files in a directory can place a practical
limit on the number of tables in a database. If the time required to open a
file in the directory increases significantly as the number of files increases,
database performance can be adversely affected.
The amount of available disk space limits the number of tables.
MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage
engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes
(2567 – 1 bytes). With this larger allowed table size, the maximum effective
table size for MySQL databases is usually determined by operating system constraints
on file sizes, not by MySQL internal limits.
The InnoDB storage engine maintains InnoDB tables within a tablespace that can
be created from several files. This allows a table to exceed the maximum individual
file size. The tablespace can include raw disk partitions, which allows extremely
large tables. The maximum tablespace size is 64TB.
The following table lists some examples of operating system file-size limits.
This is only a rough guide and is not intended to be definitive. For the most
up-to-date information, be sure to check the documentation specific to your
operating system.
Operating System File-size Limit
Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB
Explain normalization concept?
The normalization process involves getting our data to conform to three progressive
normal forms, and a higher level of normalization cannot be achieved until the
previous levels have been achieved (there are actually five normal forms, but
the last two are mainly academic and will not be discussed).
First Normal Form
The First Normal Form (or 1NF) involves removal of redundant data from horizontal
rows. We want to ensure that there is no duplication of data in a given row,
and that every column stores the least amount of information possible (making
the field atomic).
Second Normal Form
Where the First Normal Form deals with redundancy of data across a horizontal
row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns.
As stated earlier, the normal forms are progressive, so to achieve Second Normal
Form, your tables must already be in First Normal Form.
Third Normal Form
I have a confession to make; I do not often use Third Normal Form. In Third
Normal Form we are looking for data in our tables that is not fully dependant
on the primary key, but dependant on another value in the table
What’s the difference between accessing
a class method via -> and via ::?
:: is allowed to access methods that can perform static operations, i.e. those,
which do not require object initialization.
What are the advantages and disadvantages of CASCADE
STYLE SHEETS?
External Style Sheets
Advantages
Can control styles for multiple documents at once Classes can be created for
use on multiple HTML element types in many documents Selector and grouping methods
can be used to apply styles under complex contexts
Disadvantages
An extra download is required to import style information for each document
The rendering of the document may be delayed until the external style sheet
is loaded Becomes slightly unwieldy for small quantities of style definitions
Embedded Style Sheets
Advantages
Classes can be created for use on multiple tag types in the document Selector
and grouping methods can be used to apply styles under complex contexts No additional
downloads necessary to receive style information
Disadvantage
This method can not control styles for multiple documents at once
Inline Styles
Advantages
Useful for small quantities of style definitions Can override other style specification
methods at the local level so only exceptions need to be listed in conjunction
with other style methods
Disadvantages
Does not distance style information from content (a main goal of SGML/HTML)
Can not control styles for multiple documents at once Author can not create
or control classes of elements to control multiple element types within the
document Selector grouping methods can not be used to create complex element
addressing scenarios
What type of inheritance that php supports?
In PHP an extended class is always dependent on a single base class, that is,
multiple inheritance is not supported. Classes are extended using the keyword
'extends'.
How can increase the performance of MySQL select
query?
We can use LIMIT to stop MySql for further search in table after we have received
our required no. of records, also we can use LEFT JOIN or RIGHT JOIN instead
of full join in cases we have related data in two or more tables.
How can we change the name of a column of a table?
MySQL query to rename table: RENAME TABLE tbl_name TO new_tbl_name
or,
ALTER TABLE tableName CHANGE OldName newName.
When you want to show some part of a text displayed
on an HTML page in red font color? What different possibilities are there to
do this? What are the advantages/disadvantages of these methods?
There are 2 ways to show some part of a text in red:
1. Using HTML tag <font color="red">
2. Using HTML tag <span >
When viewing an HTML page in a Browser, the Browser often keeps this page in
its cache. What can be possible advantages/disadvantages of page caching? How
can you prevent caching of a certain page (please give several alternate solutions)?
When you use the metatag in the header section at the beginning of an
HTML Web page, the Web page may still be cached in the Temporary Internet Files
folder.
A page that Internet Explorer is browsing is not cached until half of the 64
KB buffer is filled. Usually, metatags are inserted in the header section of
an HTML document, which appears at the beginning of the document. When the HTML
code is parsed, it is read from top to bottom. When the metatag is read, Internet
Explorer looks for the existence of the page in cache at that exact moment.
If it is there, it is removed. To properly prevent the Web page from appearing
in the cache, place another header section at the end of the HTML document.
What are the different ways to login to a remote
server? Explain the means, advantages and disadvantages?
There is at least 3 ways to logon to a remote server:
Use ssh or telnet if you concern with security
You can also use rlogin to logon to a remote server.
Please give a regular expression (preferably Perl/PREG style), which can be
used to identify the URL from within a HTML link tag.
Try this: /href="([^"]*)"/i
How can I use the COM components in php?
The COM class provides a framework to integrate (D)COM components into your
PHP scripts.
string COM::COM( string module_name [, string server_name [, int codepage]])
- COM class constructor.
Parameters:
module_name: name or class-id of the requested component.
server_name: name of the DCOM server from which the component should be fetched.
If NULL, localhost is assumed. To allow DCOM com, allow_dcom has to be set to
TRUE in php.ini.
codepage - specifies the codepage that is used to convert php-strings to unicode-strings
and vice versa. Possible values are CP_ACP, CP_MACCP, CP_OEMCP, CP_SYMBOL, CP_THREAD_ACP,
CP_UTF7 and CP_UTF8.
Usage:
$word->Visible = 1; //open an empty document
$word->Documents->Add(); //do some weird stuff
$word->Selection->TypeText("This is a test…");
$word->Documents[1]->SaveAs("Useless test.doc"); //closing word
$word->Quit(); //free the object
$word->Release();
$word = null;
How many ways we can give the output to a browser?
HTML output
PHP, ASP, JSP, Servlet Function
Script Language output Function
Different Type of embedded Package to output to a browser
What is the default session time in php and how
can I change it?
The default session time in php is until closing of browser
What changes I have to do in php.ini file for
file uploading?
Make the following line uncomment like:
; Whether to allow HTTP file uploads.
file_uploads = On
; Temporary directory for HTTP uploaded files (will use system default if not
; specified).
upload_tmp_dir = C:\apache2triad\temp
; Maximum allowed size for uploaded files.
upload_max_filesize = 2M
How can I set a cron and how can I execute it
in Unix, Linux, and windows?
Cron is very simply a Linux module that allows you to run commands at predetermined
times or intervals. In Windows, it's called Scheduled Tasks. The name Cron is
in fact derived from the same word from which we get the word chronology, which
means order of time.
The easiest way to use crontab is via the crontab command.
# crontab
This command 'edits' the crontab. Upon employing this command, you will be
able to enter the commands that you wish to run. My version of
Linux uses the text editor vi. You can find information on using vi here.
The syntax of this file is very important – if you get it wrong, your
crontab will not function properly. The syntax of the file should be as follows:
minutes hours day_of_month month day_of_week command
All the variables, with the exception of the command itself, are numerical
constants. In addition to an asterisk (*), which is a wildcard that allows any
value, the ranges permitted for each field are as follows:
Minutes: 0-59
Hours: 0-23
Day_of_month: 1-31
Month: 1-12
Weekday: 0-6
We can also include multiple values for each entry, simply by separating each
value with a comma.
command can be any shell command and, as we will see momentarily, can also be
used to execute a Web document such as a PHP file.
So, if we want to run a script every Tuesday morning at 8:15 AM, our mycronjob
file will contain the following content on a single line:
15 8 * * 2 /path/to/scriptname
This all seems simple enough, right? Not so fast! If you try to run a PHP script
in this manner, nothing will happen (barring very special configurations that
have PHP compiled as an executable, as opposed to an Apache module). The reason
is that, in order for PHP to be parsed, it needs to be passed through Apache.
In other words, the page needs to be called via a browser or other means of
retrieving
Web content. For our purposes, I'll assume that your server configuration includes
wget, as is the case with most default configurations. To test your configuration,
log in to shell. If you're using an RPM-based system (e.g. Redhat or Mandrake),
type the following:
# wget help
If you are greeted with a wget package identification, it is installed in your
system.
You could execute the PHP by invoking wget on the URL to the page, like so:
# wget http://www.example.com/file.php
Now, let's go back to the mailstock.php file we created in the first part of
this article. We saved it in our document root, so it should be accessible via
the Internet. Remember that we wanted it to run at 4PM Eastern time, and send
you your precious closing bell report? Since I'm located in the Eastern timezone,
we can go ahead and set up our crontab to use 4:00, but if you live elsewhere,
you might have to compensate for the time difference when setting this value.
This is what my crontab will look like:
0 4 * * 1,2,3,4,5 we get http://www.example.com/mailstock.php
Steps for the payment gateway processing?
An online payment gateway is the interface between your merchant account and
your Web site. The online payment gateway allows you to immediately verify credit
card transactions and authorize funds on a customer's credit card directly from
your Web site. It then passes the transaction off to your merchant bank for
processing, commonly referred to as transaction batching
How many ways I can redirect a PHP page?
Here are the possible ways of php page redirection.
1. Using Java script:
'; echo 'window.location.href="'.$filename.'";'; echo ''; echo '';
echo ''; echo ''; } } redirect('http://maosjb.com'); ?>
2. Using php function: header("Location:http://maosjb.com ");
List out different arguments in PHP header function?
void header ( string string [, bool replace [, int http_response_code]])
What type of headers have to be added in the mail function to attach a file?
$boundary = '--' . md5( uniqid ( rand() ) );
$headers = "From: \"Me\"\n";
$headers .= "MIME-Version: 1.0\n";
$headers .= "Content-Type: multipart/mixed; boundary=\"$boundary\"";
What is the difference between Reply-to and Return-path
in the headers of a mail function?
Reply-to: Reply-to is where to delivery the reply of the mail.
Return-path: Return path is when there is a mail delivery failure occurs then
where to delivery the failure notification.
How to store the uploaded file to the final location?
move_uploaded_file ( string filename, string destination)
This function checks to ensure that the file designated by filename is a valid
upload file (meaning that it was uploaded via PHP's HTTP POST upload mechanism).
If the file is valid, it will be moved to the filename given by destination.
If filename is not a valid upload file, then no action will occur, and move_uploaded_file()
will return FALSE.
If filename is a valid upload file, but cannot be moved for some reason, no
action will occur, and move_uploaded_file() will return FALSE. Additionally,
a warning will be issued.
Explain about Type Juggling in php?
PHP does not require (or support) explicit type definition in variable declaration;
a variable's type is determined by the context in which that variable is used.
That is to say, if you assign a string value to variable $var, $var becomes
a string. If you then assign an integer value to $var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'.
If any of the operands is a float, then all operands are evaluated as floats,
and the result will be a float. Otherwise, the operands will be interpreted
as integers, and the result will also be an integer. Note that this does NOT
change the types of the operands themselves; the only change is in how the operands
are evaluated.
$foo += 2; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
If the last two examples above seem odd, see String conversion to numbers.
If you wish to change the type of a variable, see settype().
If you would like to test any of the examples in this section, you can use the
var_dump() function.
Note: The behavior of an automatic conversion to array is currently undefined.
Since PHP (for historical reasons) supports indexing into strings via offsets
using the same syntax as array indexing, the example above leads to a problem:
should $a become an array with its first element being "f", or should
"f" become the first character of the string $a? The current versions
of PHP interpret the second assignment as a string offset identification, so
$a becomes "f", the result of this automatic conversion however should
be considered undefined. PHP 4 introduced the new curly bracket syntax to access
characters in string, use this syntax instead of the one presented above:
How can I embed a java programme in php file and
what changes have to be done in php.ini file?
There are two possible ways to bridge PHP and Java: you can either integrate
PHP into a Java Servlet environment, which is the more stable and efficient
solution, or integrate Java support into PHP. The former is provided by a SAPI
module that interfaces with the Servlet server, the latter by this Java extension.
The Java extension provides a simple and effective means for creating and invoking
methods on Java objects from PHP. The JVM is created using JNI, and everything
runs in-process.
Example Code:
getProperty('java.version') . ''; echo 'Java vendor=' . $system->getProperty('java.vendor')
. ''; echo 'OS=' . $system->getProperty('os.name') . ' ' . $system->getProperty('os.version')
. ' on ' . $system->getProperty('os.arch') . ' '; // java.util.Date example
$formatter = new Java('java.text.SimpleDateFormat', "EEEE, MMMM dd, yyyy
'at' h:mm:ss a zzzz"); echo $formatter->format(new Java('java.util.Date'));
?>
The behaviour of these functions is affected by settings
in php.ini.
Table 1. Java configuration options
Name
Default
Changeable
java.class.path
NULL
PHP_INI_ALL
Name Default Changeable
java.home
NULL
PHP_INI_ALL
java.library.path
NULL
PHP_INI_ALL
java.library
JAVALIB
PHP_INI_ALL
Explain the ternary conditional operator in PHP?
Expression preceding the ? is evaluated, if it’s true, then the expression
preceding the : is executed, otherwise, the expression following : is executed.
What’s the difference between include and
require?
It’s how they handle failures. If the file is not found by require(),
it will cause a fatal error and halt the execution of the script. If the file
is not found by include(), a warning will be issued, but execution will continue.
How many ways can we get the value of current
session id?
session_id() returns the session id for the current session.
PHP 5 References
At W3Schools you will find complete references of all PHP functions:visit the w3schools website to practice.
Array functions
Calendar functions
Date functions
Directory functions
Error functions
Filesystem functions
Filter functions
FTP functions
HTTP functions
LibXML functions
Mail functions
Math functions
Misc functions
MySQLi functions
SimpleXML functions
String functions
XML Parser functions
Zip functions
MYSQL Tricks
PHP MYSQL INTERVIEW
PHP TIPS & Tricks
PHP Interview Questions, Answers [Php FAQ ]
What are the popular frameworks in PHP? Some popular PHP frameworks are:
CodeIgniter
CakePHP
Symfony
Zend Framewor Yii 2
Name the popular Content Management Systems (CMS) in PHP.
WordPress
Joomla
Magento
Drupal
What's PHP ?
The PHP Hypertext Preprocessor is a programming language that allows web developers
to create dynamic content that interacts with databases. PHP is basically used
for developing web based software applications.
What Is a Session?
A session is a logical object created by the PHP engine to allow you to preserve
data across subsequent HTTP requests.
There is only one session object available to your PHP scripts at any time.
Data saved to the session by a script can be retrieved by the same script or
another script when requested from the same visitor.
Sessions are commonly used to store temporary data to allow multiple PHP pages to offer a complete functional transaction for the same visitor.
What is meant by PEAR in php?
Answer1:
PEAR is the next revolution in PHP. This repository is bringing higher level
programming to PHP. PEAR is a framework and distribution system for reusable
PHP components. It eases installation by bringing an automated wizard, and packing
the strength and experience of PHP users into a nicely organised OOP library.
PEAR also provides a command-line interface that can be used to automatically
install "packages"
Answer2:
PEAR is short for "PHP Extension and Application Repository" and is
pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the governing body.
The project has been founded by Stig S. Bakken in 1999 and quite a lot of people
have joined the project since then.
How can we know the number of days between two given dates using PHP?
Simple arithmetic:
$date1 = date('Y-m-d');
$date2 = '2006-07-01';
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo "Number of days since '2006-07-01': $days";
How can we repair a MySQL table?
The syntex for repairing a mysql table is:
REPAIR TABLE tablename
REPAIR TABLE tablename QUICK
REPAIR TABLE tablename EXTENDED
This command will repair the table specified.
If QUICK is given, MySQL will do a repair of only the index tree.
If EXTENDED is given, it will create index row by row.
What is the difference between $message and $$message?
Anwser 1:
$message is a simple variable whereas $$message is a reference variable. Example:
$user = 'bob'
is equivalent to
$holder = 'user';
$$holder = 'bob';
Anwser 2:
They are both variables. But $message is a variable with a fixed name. $$message
is a variable who's name is stored in $message. For example, if $message contains
"var", $$message is the same as $var.
What Is a Persistent Cookie?
A persistent cookie is a cookie which is stored in a cookie file permanently
on the browser's computer. By default, cookies are created as temporary cookies
which stored only in the browser's memory. When the browser is closed, temporary
cookies will be erased. You should decide when to use temporary cookies and
when to use persistent cookies based on their differences:
*Temporary cookies can not be used for tracking long-term information.
*Persistent cookies can be used for tracking long-term information.
*Temporary cookies are safer because no programs other than the browser can
access them.
*Persistent cookies are less secure because users can open cookie files see
the cookie values.
What does a special set of tags <?= and ?>
do in PHP?
The output is displayed directly to the browser.
How do you define a constant?
Via define() directive, like define ("MYCONSTANT", 100);
What are the differences between require and include,
include_once?
Anwser 1:
require_once() and include_once() are both the functions to include and evaluate
the specified file only once. If the specified file is included previous to
the present call occurrence, it will not be done again.
But require() and include() will do it as many times they are asked to do.
Anwser 2:
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include() statement,
with the only difference being that if the code from a file has already been
included, it will not be included again. The major difference between include()
and require() is that in failure include() produces a warning message whereas
require() produces a fatal errors.
Anwser 3:
All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include()
does not.
The include_once() statement includes and evaluates the specified file during
the execution of the script. This is a behavior similar to the include() statement,
with the only difference being that if the code from a file has already been
included, it will not be included again. It des not call a fatal error if file
not exists. require_once() does the same as include_once(), but it calls a fatal
error if file not exists.
Anwser 4:
File will not be included more than once. If we want to include a file once
only and further calling of the file will be ignored then we have to use the
PHP function include_once(). This will prevent problems with function redefinitions,
variable value reassignments, etc.
What is meant by urlencode and urldecode?
Anwser 1:
urlencode() returns the URL encoded version of the given string. URL coding
converts special characters into % signs followed by two hex digits. For example:
urlencode("10.00%") will return "10%2E00%25". URL encoded
strings are safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.
Anwser 2:
string urlencode(str) - Returns the URL encoded version of the input string.
String values to be used in URL query string need to be URL encoded. In the
URL encoded version:
Alphanumeric characters are maintained as is.
Space characters are converted to "+" characters.
Other non-alphanumeric characters are converted "%" followed by two
hex digits representing the converted character.
string urldecode(str) - Returns the original string of the input URL encoded
string.
For example:
$discount ="10.00%";
$url = "http://domain.com/submit.php?disc=".urlencode($discount);
echo $url;
You will get "http://domain.com/submit.php?disc=10%2E00%25".
How To Get the Uploaded File Information in the
Receiving Script?
Once the Web server received the uploaded file, it will call the PHP script
specified in the form action attribute to process them. This receiving PHP script
can get the uploaded file information through the predefined array called $_FILES.
Uploaded file information is organized in $_FILES as a two-dimensional array
as:
$_FILES[$fieldName]['name'] - The Original file name on the browser system.
$_FILES[$fieldName]['type'] - The file type determined by the browser.
$_FILES[$fieldName]['size'] - The Number of bytes of the file content.
$_FILES[$fieldName]['tmp_name'] - The temporary filename of the file in which
the uploaded file was stored on the server.
$_FILES[$fieldName]['error'] - The error code associated with this file upload.
The $fieldName is the name used in the <INPUT TYPE=FILE, NAME=fieldName>.
What is the difference between mysql_fetch_object
and mysql_fetch_array?
MySQL fetch object will collect first single matching record where mysql_fetch_array
will collect all matching records from the table in an array
How can I execute a PHP script using command line?
Just run the PHP CLI (Command Line Interface) program and provide the PHP script
file name as the command line argument. For example, "php myScript.php",
assuming "php" is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may
not execute properly in command line environment.
I am trying to assign a variable the value of 0123, but it keeps coming up with
a different number, what’s the problem?
PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar
PHP interview questions for more numeric problems.
Would I use print "$a dollars" or "{$a}
dollars" to print out the amount of dollars in this example?
In this example it wouldn’t matter, since the variable is all by itself,
but if you were to print something like "{$a},000,000 mln dollars",
then you definitely need to use the braces.
What are the different tables present in MySQL?
Which type of table is generated when we are creating a table in the following
syntax: create table employee(eno int(2),ename varchar(10))?
Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23. When you fire the above
create query MySQL will create a MyISAM table.
How To Create a Table?
If you want to create a table, you can run the CREATE TABLE statement as shown
in the following sample script:
<?php
include "mysql_connection.php";
$sql = "CREATE TABLE Tech_links ("
. " id INTEGER NOT NULL"
. ", url VARCHAR(80) NOT NULL"
. ", notes VARCHAR(1024)"
. ", counts INTEGER"
. ", time TIMESTAMP DEFAULT sysdate()"
. ")";
if (mysql_query($sql, $con)) {
print("Table Tech_links created.\n");
} else {
print("Table creation failed.\n");
}
mysql_close($con);
?>
Remember that mysql_query() returns TRUE/FALSE on CREATE statements. If you
run this script, you will get something like this:
Table Tech_links created.
How can we encrypt the username and password using
PHP?
Answer1
You can encrypt a password with the following Mysql>SET PASSWORD=PASSWORD("Password");
Answer2
You can use the MySQL PASSWORD() function to encrypt username and password.
For example,
INSERT into user (password, ...) VALUES (PASSWORD($password”)), ...);
How do you pass a variable by value?
Just like in C++, put an ampersand in front of it, like $a = &$b
What is the functionality of the functions STRSTR()
and STRISTR()?
string strstr ( string haystack, string needle ) returns part of haystack string
from the first occurrence of needle to the end of haystack. This function is
case-sensitive.
stristr() is idential to strstr() except that it is case insensitive.
When are you supposed to use endif to end the
conditional statement?
When the original if was followed by : and then the code block without braces.
How can we send mail using JavaScript?
No. There is no way to send emails directly using JavaScript.
But you can use JavaScript to execute a client side email program send the
email using the "mailto" code. Here is an example:
function myfunction(form)
{
tdata=document.myform.tbox1.value;
location="mailto:mailid@domain.com?subject=...";
return true;
}
What is the functionality of the function strstr
and stristr?
strstr() returns part of a given string from the first occurrence of a given
substring to the end of the string. For example: strstr("user@example.com","@")
will return "@example.com".
stristr() is idential to strstr() except that it is case insensitive.
What is the difference between ereg_replace()
and eregi_replace()?
eregi_replace() function is identical to ereg_replace() except that it ignores
case distinction when matching alphabetic characters.
How do I find out the number of parameters passed into function9. ?
func_num_args() function returns the number of parameters passed in.
What is the purpose of the following files having
extensions: frm, myd, and myi? What these files contain?
In MySQL, the default table type is MyISAM.
Each MyISAM table is stored on disk in three files. The files have names that
begin with the table name and have an extension to indicate the file type.
The '.frm' file stores the table definition.
The data file has a '.MYD' (MYData) extension.
The index file has a '.MYI' (MYIndex) extension,
If the variable $a is equal to 5 and variable $b is equal to character a, what’s
the value of $$b?
100, it’s a reference to existing variable.
How To Protect Special Characters in Query String?
If you want to include special characters like spaces in the query string, you
need to protect them by applying the urlencode() translation function. The script
below shows how to use urlencode():
<?php
print("<html>");
print("<p>Please click the links below"
." to submit comments about TECHPreparation.com:</p>");
$comment = 'I want to say: "It\'s a good site! :->"';
$comment = urlencode($comment);
print("<p>"
."<a href=\"processing_forms.php?name=Guest&comment=$comment\">"
."It's an excellent site!</a></p>");
$comment = 'This visitor said: "It\'s an average site! :-("';
$comment = urlencode($comment);
print("<p>"
.'<a href="processing_forms.php?'.$comment.'">'
."It's an average site.</a></p>");
print("</html>");
?>
Are objects passed by value or by reference?
Everything is passed by value.
What are the differences between DROP a table
and TRUNCATE a table?
DROP TABLE table_name - This will delete the table and its data.
TRUNCATE TABLE table_name - This will delete the data of the table, but not
the table definition.
How do you call a constructor for a parent class?
parent::constructor($value)
WHAT ARE THE DIFFERENT TYPES OF ERRORS IN PHP?
Here are three basic types of runtime errors in PHP:
1. Notices: These are trivial, non-critical errors that PHP encounters while
executing a script - for example, accessing a variable that has not yet been
defined. By default, such errors are not displayed to the user at all - although
you can change this default behavior.
2. Warnings: These are more serious errors - for example, attempting to include()
a file which does not exist. By default, these errors are displayed to the user,
but they do not result in script termination.
3. Fatal errors: These are critical errors - for example, instantiating an
object of a non-existent class, or calling a non-existent function. These errors
cause the immediate termination of the script, and PHP's default behavior is
to display them to the user when they take place.
Internally, these variations are represented by twelve different error types
What’s the special meaning of __sleep and __wakeup?
__sleep returns the array of all the variables than need to be saved, while
__wakeup retrieves them.
How can we submit a form without a submit button?
If you don't want to use the Submit button to submit a form, you can use normal
hyper links to submit a form. But you need to use some JavaScript code in the
URL of the link. For example:
<a href="javascript: document.myform.submit();">Submit Me</a>
How can we register the variables into a session?
session_register($session_var);
$_SESSION['var'] = 'value';
What is the difference between characters \023 and \x23?
The first one is octal 23, the second is hex 23.
With a heredoc syntax, do I get variable substitution inside the heredoc contents?
Yes.
How can we submit form without a submit button?
We can use a simple JavaScript code linked to an event trigger of any form field.
In the JavaScript code, we can call the document.form.submit() function to submit
the form. For example: <input type=button value="Save" onClick="document.form.submit()">
How can we create a database using PHP and mysql?
We can create MySQL database with the use of mysql_create_db($databaseName)
to create a database.
How many ways we can retrieve the date in result set of mysql using php?
As individual objects so single record or as a set or arrays.
Can we use include ("abc.php") two times
in a php page "makeit.php"?
Yes.
For printing out strings, there are echo, print and printf. Explain the differences.
echo is the most primitive of them, and just outputs the contents following
the construct to the screen. print is also a construct (so parentheses are optional
when calling it), but it returns TRUE on successful output and FALSE if it was
unable to print out the string. However, you can pass multiple parameters to
echo, like:
<?php echo 'Welcome ', 'to', ' ', 'techpreparations!'; ?>
and it will output the string "Welcome to techpreparations!" print
does not take multiple parameters. It is also generally argued that echo is
faster, but usually the speed advantage is negligible, and might not be there
for future versions of PHP. printf is a function, not a construct, and allows
such advantages as formatted output, but it’s the slowest way to print
out data out of echo, print and printf.
I am writing an application in PHP that outputs a printable version of driving
directions. It contains some long sentences, and I am a neat freak, and would
like to make sure that no line exceeds 50 characters. How do I accomplish that
with PHP?
On large strings that need to be formatted according to some length specifications,
use wordwrap() or chunk_split().
What’s the output of the ucwords function in this example?
$formatted = ucwords("TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS");
print $formatted;
What will be printed is TECHPREPARATIONS IS COLLECTION OF INTERVIEW QUESTIONS.
ucwords() makes every first letter of every word capital, but it does not lower-case
anything else. To avoid this, and get a properly formatted string, it’s
worth using strtolower() first.
What’s the difference between htmlentities() and htmlspecialchars()?
htmlspecialchars only takes care of <, >, single quote ‘, double
quote " and ampersand. htmlentities translates all occurrences of character
sequences that have different meaning in HTML.
How can we extract string "abc.com" from a string "mailto:info@abc.com?subject=Feedback"
using regular expression of PHP?
$text = "mailto:info@abc.com?subject=Feedback";
preg_match('.*@([^?]*)', $text, $output);
echo $output[1];
Note that the second index of $output, $output[1], gives the match, not the
first one, $output[0].
So if md5() generates the most secure hash, why would you ever use the less
secure crc32() and sha1()?
Crypto usage in PHP is simple, but that doesn’t mean it’s free.
First off, depending on the data that you’re encrypting, you might have
reasons to store a 32-bit value in the database instead of the 160-bit value
to save on space. Second, the more secure the crypto is, the longer is the computation
time to deliver the hash value. A high volume site might be significantly slowed
down, if frequent md5() generation is required.
How can we destroy the session, how can we unset the variable of a session?
session_unregister() - Unregister a global variable from the current session
session_unset() - Free all session variables
What are the different functions in sorting an
array?
Sorting functions in PHP:
asort()
arsort()
ksort()
krsort()
uksort()
sort()
natsort()
rsort()
How can we know the count/number of elements of
an array?
2 ways:
a) sizeof($array) - This function is an alias of count()
b) count($urarray) - This function returns the number of elements in an array.
Interestingly if you just pass a simple var instead of an array, count() will
return 1.
How many ways we can pass the variable through
the navigation between the pages?
At least 3 ways:
1. Put the variable into session in the first page, and get it back from session
in the next page.
2. Put the variable into cookie in the first page, and get it back from the
cookie in the next page.
3. Put the variable into a hidden form field, and get it back from the form
in the next page.
What is the maximum length of a table name, a
database name, or a field name in MySQL?
Database name: 64 characters
Table name: 64 characters
Column name: 64 characters
How many values can the SET function of MySQL
take?
MySQL SET function can take zero or more values, but at the maximum it can take
64 values.
What are the other commands to know the structure
of a table using MySQL commands except EXPLAIN command?DESCRIBE table_name;
How can we find the number of rows in a table
using MySQL?
Use this for MySQL
SELECT COUNT(*) FROM table_name;
What’s the difference between md5(), crc32()
and sha1() crypto on PHP?
The major difference is the length of the hash generated. CRC32 is, evidently,
32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value.
This is important when avoiding collisions.
How can we find the number of rows in a result
set using PHP?
Here is how can you find the number of rows in a result set in PHP:
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";
How many ways we can we find the current date
using MySQL?
SELECT CURDATE();
SELECT CURRENT_DATE();
SELECT CURTIME();
SELECT CURRENT_TIME();
Give the syntax of GRANT commands?
The generic syntax for GRANT is as following
GRANT [rights] on [database] TO [username@hostname] IDENTIFIED BY [password]
Now rights can be:
a) ALL privilages
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all databse by usingh *.* or some specific database
by database.* or a specific table by database.table_name.
Give the syntax of REVOKE commands?
The generic syntax for revoke is as following
REVOKE [rights] on [database] FROM [username@hostname]
Now rights can be:
a) ALL privileges
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all database by using *.* or some specific database
by database.* or a specific table by database.table_name.
What is the difference between CHAR and VARCHAR data types?
CHAR is a fixed length data type. CHAR(n) will take n characters of storage
even if you enter less than n characters to that column. For example, "Hello!"
will be stored as "Hello! " in CHAR(10) column.
VARCHAR is a variable length data type. VARCHAR(n) will take only the required
storage for the actual number of characters entered to that column. For example,
"Hello!" will be stored as "Hello!" in VARCHAR(10) column.
How can we encrypt and decrypt a data present in a mysql table using mysql?
AES_ENCRYPT() and AES_DECRYPT()
Will comparison of string "10" and integer
11 work in PHP?
Yes, internally PHP will cast everything to the integer type, so numbers 10
and 11 will be compared.
What is the functionality of MD5 function in PHP?
string md5(string)
It calculates the MD5 hash of a string. The hash is a 32-character hexadecimal
number.
How can I load data from a text file into a table?
The MySQL provides a LOAD DATA INFILE command. You can load data from a file.
Great tool but you need to make sure that:
a) Data must be delimited
b) Data fields must match table columns correctly
How can we know the number of days between two
given dates using MySQL?
Use DATEDIFF()
SELECT DATEDIFF(NOW(),'2006-07-01');
How can we change the name of a column of a table?
This will change the name of column:
ALTER TABLE table_name CHANGE old_colm_name new_colm_name
How can we change the data type of a column of a table?
This will change the data type of a column:
ALTER TABLE table_name CHANGE colm_name same_colm_name [new data type]
What is the difference between GROUP BY and ORDER BY in SQL?
To sort a result, use an ORDER BY clause.
The most general way to satisfy a GROUP BY clause is to scan the whole table
and create a new temporary table where all rows from each group are consecutive,
and then use this temporary table to discover groups and apply aggregate functions
(if any).
ORDER BY [col1],[col2],...[coln]; Tells DBMS according to what columns it should
sort the result. If two rows will have the same value in col1 it will try to
sort them according to col2 and so on.
GROUP BY [col1],[col2],...[coln]; Tells DBMS to group (aggregate) results with
same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with
it, if you want to count all items in group, sum all values or view average.
What is meant by MIME?
Answer 1:
MIME is Multipurpose Internet Mail Extensions is an Internet standard for the
format of e-mail. However browsers also uses MIME standard to transmit files.
MIME has a header which is added to a beginning of the data. When browser sees
such header it shows the data as it would be a file (for example image)
Some examples of MIME types:
audio/x-ms-wmp
image/png
application/x-shockwave-flash
Answer 2:
Multipurpose Internet Mail Extensions.
WWW's ability to recognize and handle files of different types is largely dependent
on the use of the MIME (Multipurpose Internet Mail Extensions) standard. The
standard provides for a system of registration of file types with information
about the applications needed to process them. This information is incorporated
into Web server and browser software, and enables the automatic recognition
and display of registered file types. …
How can we know that a session is started or not?
A session starts by session_start() function.
This session_start() is always declared in header portion. it always declares
first. then we write session_register().
What are the differences between mysql_fetch_array(), mysql_fetch_object(),
mysql_fetch_row()?
Answer 1:
mysql_fetch_array() -> Fetch a result row as a combination of associative
array and regular array.
mysql_fetch_object() -> Fetch a result row as an object.
mysql_fetch_row() -> Fetch a result set as a regular array().
Answer 2:
The difference between mysql_fetch_row() and mysql_fetch_array() is that the
first returns the results in a numeric array ($row[0], $row[1], etc.), while
the latter returns a the results an array containing both numeric and associative
keys ($row['name'], $row['email'], etc.). mysql_fetch_object() returns an object
($row->name, $row->email, etc.).
If we login more than one browser windows at the same time with same user and
after that we close one window, then is the session is exist to other windows
or not? And if yes then why? If no then why?
Session depends on browser. If browser is closed then session is lost. The session
data will be deleted after session time out. If connection is lost and you recreate
connection, then session will continue in the browser.
What are the MySQL database files stored in system
?
Data is stored in name.myd
Table structure is stored in name.frm
Index is stored in name.myi
What is the difference between PHP4 and PHP5?
PHP4 cannot support oops concepts and Zend engine 1 is used.
PHP5 supports oops concepts and Zend engine 2 is used.
Error supporting is increased in PHP5.
XML and SQLLite will is increased in PHP5.
Can we use include(abc.PHP) two times in a PHP
page makeit.PHP”?
Yes we can include that many times we want, but here are some things to make
sure of:
(including abc.PHP, the file names are case-sensitive)
there shouldn't be any duplicate function names, means there should not be functions
or classes or variables with the same name in abc.PHP and makeit.php
What are the differences between mysql_fetch_array(),
mysql_fetch_object(), mysql_fetch_row()?
mysql_fetch_array - Fetch a result row as an associative array and a numeric
array.
mysql_fetch_object - Returns an object with properties that correspond to the
fetched row and moves the internal data pointer ahead. Returns an object with
properties that correspond to the fetched row, or FALSE if there are no more
rows
mysql_fetch_row() - Fetches one row of data from the result associated with
the specified result identifier. The row is returned as an array. Each result
column is stored in an array offset, starting at offset 0.
What is meant by nl2br()?
Anwser1:
nl2br() inserts a HTML tag <br> before all new line characters \n in a
string.
echo nl2br("god bless \n you");
output:
god bless<br>
you
How can we encrypt and decrypt a data presented
in a table using MySQL?
You can use functions: AES_ENCRYPT() and AES_DECRYPT() like:
AES_ENCRYPT(str, key_str)
AES_DECRYPT(crypt_str, key_str)
How can I retrieve values from one database server
and store them in other database server using PHP?
For this purpose, you can first read the data from one server into session variables.
Then connect to other server and simply insert the data into the database.
Who is the father of PHP and what is the current version of PHP and MYSQL?
Rasmus Lerdorf.
PHP 5.1. Beta
MySQL 5.0
In how many ways we can retrieve data in the result set of MYSQL using
PHP?
mysql_fetch_array - Fetch a result row as an associative array, a numeric array,
or both
mysql_fetch_assoc - Fetch a result row as an associative array
mysql_fetch_object - Fetch a result row as an object
mysql_fetch_row —- Get a result row as an enumerated array
What are the functions for IMAP?
imap_body - Read the message body
imap_check - Check current mailbox
imap_delete - Mark a message for deletion from current mailbox
imap_mail - Send an email message
What are encryption functions in PHP?
CRYPT()
MD5()
What is the difference between htmlentities() and htmlspecialchars()?
htmlspecialchars() - Convert some special characters to HTML entities (Only
the most widely used)
htmlentities() - Convert ALL special characters to HTML entities
What is the functionality of the function htmlentities?
htmlentities() - Convert all applicable characters to HTML entities
This function is identical to htmlspecialchars() in all ways, except with htmlentities(),
all characters which have HTML character entity equivalents are translated into
these entities.
How can we get the properties (size, type, width,
height) of an image using php image functions?
To know the image size use getimagesize() function
To know the image width use imagesx() function
To know the image height use imagesy() function
How can we increase the execution time of a php script?
By the use of void set_time_limit(int seconds)
Set the number of seconds a script is allowed to run. If this is reached, the
script returns a fatal error. The default limit is 30 seconds or, if it exists,
the max_execution_time value defined in the php.ini. If seconds is set to zero,
no time limit is imposed.
When called, set_time_limit() restarts the timeout counter from zero. In other
words, if the timeout is the default 30 seconds, and 25 seconds into script
execution a call such as set_time_limit(20) is made, the script will run for
a total of 45 seconds before timing out.
HOW CAN WE TAKE A BACKUP OF A MYSQL TABLE AND
HOW CAN WE RESTORE IT?
Answer 1:
Create a full backup of your database: shell> mysqldump tab=/path/to/some/dir
opt db_name
Or: shell> mysqlhotcopy db_name /path/to/some/dir
The full backup file is just a set of SQL statements, so restoring it is very
easy:
shell> mysql "."Executed";
Answer 2:
To backup: BACKUP TABLE tbl_name TO /path/to/backup/directory
’ To restore: RESTORE TABLE tbl_name FROM /path/to/backup/directory
mysqldump: Dumping Table Structure and Data
Utility to dump a database or a collection of database for backup or for transferring
the data to another SQL server (not necessarily a MySQL server). The dump will
contain SQL statements to create the table and/or populate the table.
-t, no-create-info
Don't write table creation information (the CREATE TABLE statement).
-d, no-data
Don't write any row information for the table. This is very useful if you just
want to get a dump of the structure for a table!
How to set cookies?
setcookie('variable','value','time')
;
variable - name of the cookie variable
value - value of the cookie variable
time - expiry time
Example: setcookie('Test',$i,time()+3600);
Test - cookie variable name
$i - value of the variable 'Test'
time()+3600 - denotes that the cookie will expire after an one hour
How to reset/destroy a cookie ?
Reset a cookie by specifying expire time in the past:
Example: setcookie('Test',$i,time()-3600); // already expired time
Reset a cookie by specifying its name only
Example: setcookie('Test');
What types of images that PHP supports ?
Using imagetypes() function to find out what types of images are supported in
your PHP engine.
imagetypes() - Returns the image types supported.
This function returns a bit-field corresponding to the image formats supported
by the version of GD linked into PHP. The following bits are returned, IMG_GIF
IMG_JPG IMG_PNG IMG_WBMP IMG_XPM.
Check if a variable is an integer in JAVASCRIPT ?
var myValue =9.8;
if(parseInt(myValue)== myValue)
alert('Integer');
else
alert('Not an integer');
Tools used for drawing ER diagrams.
Case Studio
Smart Draw
How can I know that a variable is a number or not using
a JavaScript?
Answer 1:
bool is_numeric( mixed var)
Returns TRUE if var is a number or a numeric string, FALSE otherwise.
Answer 2:
Definition and Usage
The isNaN() function is used to check if a value is not a number.
Syntax
isNaN(number)
Parameter Description
number Required. The value to be tested
How can we submit from without a submit button?
Trigger the JavaScript code on any event ( like onSelect of drop down list box,
onfocus, etc ) document.myform.submit(); This will submit the form.
How many ways can we get the value of current session id?
session_id() returns the session id for the current session.
How can we destroy the cookie?
Set the cookie with a past expiration time.
What are the current versions of Apache, PHP, and MySQL?
PHP: PHP 5.1.2
MySQL: MySQL 5.1
Apache: Apache 2.1
What are the reasons for selecting LAMP (Linux,
Apache, MySQL, Php) instead of combination of other software programs, servers
and operating systems?
All of those are open source resource. Security of Linux is very more
than windows. Apache is a better server that IIS both in functionality and security.
Mysql is world most popular open source database. Php is more faster that asp
or any other scripting language.
What are the features and advantages of OBJECT
ORIENTED PROGRAMMING?
One of the main advantages of OO programming is its ease of modification; objects
can easily be modified and added to a system there by reducing maintenance costs.
OO programming is also considered to be better at modeling the real world than
is procedural programming. It allows for more complicated and flexible interactions.
OO systems are also easier for non-technical personnel to understand and easier
for them to participate in the maintenance and enhancement of a system because
it appeals to natural human cognition patterns. For some systems, an OO approach
can speed development time since many objects are standard across systems and
can be reused. Components that manage dates, shipping, shopping carts, etc.
can be purchased and easily modified for a specific system.
How can we get second of the current time using
date function?
$second = date("s");
What is the use of friend function?
Friend functions
Sometimes a function is best shared among a number of different classes. Such
functions can be declared either as member functions of one class or as global
functions. In either case they can be set to be friends of other classes, by
using a friend specifier in the class that is admitting them. Such functions
can use all attributes of the class which names them as a friend, as if they
were themselves members of that class.
A friend declaration is essentially a prototype for a member function, but instead
of requiring an implementation with the name of that class attached by the double
colon syntax, a global function or member function of another class provides
the match.
class mylinkage
{
private:
mylinkage * prev;
mylinkage * next;
protected:
friend void set_prev(mylinkage* L, mylinkage* N);
void set_next(mylinkage* L);
public:
mylinkage * succ();
mylinkage * pred();
mylinkage();
};
void mylinkage::set_next(mylinkage* L) { next = L; }
void set_prev(mylinkage * L, mylinkage * N ) { N->prev = L; }
Friends in other classes
It is possible to specify a member function of another class as a friend as
follows:
class C
{
friend int B::f1();
};
class B
{
int f1();
};
It is also possible to specify all the functions in another class as friends,
by specifying the entire class as a friend.
class A
{
friend class B;
};
Friend functions allow binary operators to be defined which combine private
data in a pair of objects. This is particularly powerful when using the operator
overloading features of C++. We will return to it when we look at overloading.
How can we get second of the current time using date function?
$second = date("s");
What is the maximum size of a file that can be uploaded using PHP and how can
we change this?
You can change maximum size of a file set upload_max_filesize variable in php.ini
file
How can I make a script that can be bilingual
(supports English, German)?
You can change char set variable in above line in the script to support bi language.
What are the difference between abstract class and interface?
Abstract class: abstract classes are the class where one or more methods are
abstract but not necessarily all method has to be abstract. Abstract methods
are the methods, which are declare in its class but not define. The definition
of those methods must be in its extending class.
Interface: Interfaces are one type of class where all the methods are abstract.
That means all the methods only declared but not defined. All the methods must
be define by its implemented class.
What are the advantages of stored procedures,
triggers, indexes?
A stored procedure is a set of SQL commands that can be compiled and stored
in the server. Once this has been done, clients don't need to keep re-issuing
the entire query but can refer to the stored procedure. This provides better
overall performance because the query has to be parsed only once, and less information
needs to be sent between the server and the client. You can also raise the conceptual
level by having libraries of functions in the server. However, stored procedures
of course do increase the load on the database server system, as more of the
work is done on the server side and less on the client (application) side. Triggers
will also be implemented. A trigger is effectively a type of stored procedure,
one that is invoked when a particular event occurs. For example, you can install
a stored procedure that is triggered each time a record is deleted from a transaction
table and that stored procedure automatically deletes the corresponding customer
from a customer table when all his transactions are deleted. Indexes are used
to find rows with specific column values quickly. Without an index, MySQL must
begin with the first row and then read through the entire table to find the
relevant rows. The larger the table, the more this costs. If the table has an
index for the columns in question, MySQL can quickly determine the position
to seek to in the middle of the data file without having to look at all the
data. If a table has 1,000 rows, this is at least 100 times faster than reading
sequentially. If you need to access most of the rows, it is faster to read sequentially,
because this minimizes disk seeks.
What is maximum size of a database in mysql?
If the operating system or filesystem places a limit on the number of files
in a directory, MySQL is bound by that constraint. The efficiency of the operating
system in handling large numbers of files in a directory can place a practical
limit on the number of tables in a database. If the time required to open a
file in the directory increases significantly as the number of files increases,
database performance can be adversely affected.
The amount of available disk space limits the number of tables.
MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage
engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes
(2567 – 1 bytes). With this larger allowed table size, the maximum effective
table size for MySQL databases is usually determined by operating system constraints
on file sizes, not by MySQL internal limits.
The InnoDB storage engine maintains InnoDB tables within a tablespace that can
be created from several files. This allows a table to exceed the maximum individual
file size. The tablespace can include raw disk partitions, which allows extremely
large tables. The maximum tablespace size is 64TB.
The following table lists some examples of operating system file-size limits.
This is only a rough guide and is not intended to be definitive. For the most
up-to-date information, be sure to check the documentation specific to your
operating system.
Operating System File-size Limit
Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 filesystem) 4TB
Solaris 9/10 16TB
NetWare w/NSS filesystem 8TB
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
MacOS X w/ HFS+ 2TB
Explain normalization concept?
The normalization process involves getting our data to conform to three progressive
normal forms, and a higher level of normalization cannot be achieved until the
previous levels have been achieved (there are actually five normal forms, but
the last two are mainly academic and will not be discussed).
First Normal Form
The First Normal Form (or 1NF) involves removal of redundant data from horizontal
rows. We want to ensure that there is no duplication of data in a given row,
and that every column stores the least amount of information possible (making
the field atomic).
Second Normal Form
Where the First Normal Form deals with redundancy of data across a horizontal
row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns.
As stated earlier, the normal forms are progressive, so to achieve Second Normal
Form, your tables must already be in First Normal Form.
Third Normal Form
I have a confession to make; I do not often use Third Normal Form. In Third
Normal Form we are looking for data in our tables that is not fully dependant
on the primary key, but dependant on another value in the table
What’s the difference between accessing
a class method via -> and via ::?
:: is allowed to access methods that can perform static operations, i.e. those,
which do not require object initialization.
What are the advantages and disadvantages of CASCADE
STYLE SHEETS?
External Style Sheets
Advantages
Can control styles for multiple documents at once Classes can be created for
use on multiple HTML element types in many documents Selector and grouping methods
can be used to apply styles under complex contexts
Disadvantages
An extra download is required to import style information for each document
The rendering of the document may be delayed until the external style sheet
is loaded Becomes slightly unwieldy for small quantities of style definitions
Embedded Style Sheets
Advantages
Classes can be created for use on multiple tag types in the document Selector
and grouping methods can be used to apply styles under complex contexts No additional
downloads necessary to receive style information
Disadvantage
This method can not control styles for multiple documents at once
Inline Styles
Advantages
Useful for small quantities of style definitions Can override other style specification
methods at the local level so only exceptions need to be listed in conjunction
with other style methods
Disadvantages
Does not distance style information from content (a main goal of SGML/HTML)
Can not control styles for multiple documents at once Author can not create
or control classes of elements to control multiple element types within the
document Selector grouping methods can not be used to create complex element
addressing scenarios
What type of inheritance that php supports?
In PHP an extended class is always dependent on a single base class, that is,
multiple inheritance is not supported. Classes are extended using the keyword
'extends'.
How can increase the performance of MySQL select
query?
We can use LIMIT to stop MySql for further search in table after we have received
our required no. of records, also we can use LEFT JOIN or RIGHT JOIN instead
of full join in cases we have related data in two or more tables.
How can we change the name of a column of a table?
MySQL query to rename table: RENAME TABLE tbl_name TO new_tbl_name
or,
ALTER TABLE tableName CHANGE OldName newName.
When you want to show some part of a text displayed
on an HTML page in red font color? What different possibilities are there to
do this? What are the advantages/disadvantages of these methods?
There are 2 ways to show some part of a text in red:
1. Using HTML tag <font color="red">
2. Using HTML tag <span >
When viewing an HTML page in a Browser, the Browser often keeps this page in
its cache. What can be possible advantages/disadvantages of page caching? How
can you prevent caching of a certain page (please give several alternate solutions)?
When you use the metatag in the header section at the beginning of an
HTML Web page, the Web page may still be cached in the Temporary Internet Files
folder.
A page that Internet Explorer is browsing is not cached until half of the 64
KB buffer is filled. Usually, metatags are inserted in the header section of
an HTML document, which appears at the beginning of the document. When the HTML
code is parsed, it is read from top to bottom. When the metatag is read, Internet
Explorer looks for the existence of the page in cache at that exact moment.
If it is there, it is removed. To properly prevent the Web page from appearing
in the cache, place another header section at the end of the HTML document.
What are the different ways to login to a remote
server? Explain the means, advantages and disadvantages?
There is at least 3 ways to logon to a remote server:
Use ssh or telnet if you concern with security
You can also use rlogin to logon to a remote server.
Please give a regular expression (preferably Perl/PREG style), which can be
used to identify the URL from within a HTML link tag.
Try this: /href="([^"]*)"/i
How can I use the COM components in php?
The COM class provides a framework to integrate (D)COM components into your
PHP scripts.
string COM::COM( string module_name [, string server_name [, int codepage]])
- COM class constructor.
Parameters:
module_name: name or class-id of the requested component.
server_name: name of the DCOM server from which the component should be fetched.
If NULL, localhost is assumed. To allow DCOM com, allow_dcom has to be set to
TRUE in php.ini.
codepage - specifies the codepage that is used to convert php-strings to unicode-strings
and vice versa. Possible values are CP_ACP, CP_MACCP, CP_OEMCP, CP_SYMBOL, CP_THREAD_ACP,
CP_UTF7 and CP_UTF8.
Usage:
$word->Visible = 1; //open an empty document
$word->Documents->Add(); //do some weird stuff
$word->Selection->TypeText("This is a test…");
$word->Documents[1]->SaveAs("Useless test.doc"); //closing word
$word->Quit(); //free the object
$word->Release();
$word = null;
How many ways we can give the output to a browser?
HTML output
PHP, ASP, JSP, Servlet Function
Script Language output Function
Different Type of embedded Package to output to a browser
What is the default session time in php and how
can I change it?
The default session time in php is until closing of browser
What changes I have to do in php.ini file for
file uploading?
Make the following line uncomment like:
; Whether to allow HTTP file uploads.
file_uploads = On
; Temporary directory for HTTP uploaded files (will use system default if not
; specified).
upload_tmp_dir = C:\apache2triad\temp
; Maximum allowed size for uploaded files.
upload_max_filesize = 2M
How can I set a cron and how can I execute it
in Unix, Linux, and windows?
Cron is very simply a Linux module that allows you to run commands at predetermined
times or intervals. In Windows, it's called Scheduled Tasks. The name Cron is
in fact derived from the same word from which we get the word chronology, which
means order of time.
The easiest way to use crontab is via the crontab command.
# crontab
This command 'edits' the crontab. Upon employing this command, you will be
able to enter the commands that you wish to run. My version of
Linux uses the text editor vi. You can find information on using vi here.
The syntax of this file is very important – if you get it wrong, your
crontab will not function properly. The syntax of the file should be as follows:
minutes hours day_of_month month day_of_week command
All the variables, with the exception of the command itself, are numerical
constants. In addition to an asterisk (*), which is a wildcard that allows any
value, the ranges permitted for each field are as follows:
Minutes: 0-59
Hours: 0-23
Day_of_month: 1-31
Month: 1-12
Weekday: 0-6
We can also include multiple values for each entry, simply by separating each
value with a comma.
command can be any shell command and, as we will see momentarily, can also be
used to execute a Web document such as a PHP file.
So, if we want to run a script every Tuesday morning at 8:15 AM, our mycronjob
file will contain the following content on a single line:
15 8 * * 2 /path/to/scriptname
This all seems simple enough, right? Not so fast! If you try to run a PHP script
in this manner, nothing will happen (barring very special configurations that
have PHP compiled as an executable, as opposed to an Apache module). The reason
is that, in order for PHP to be parsed, it needs to be passed through Apache.
In other words, the page needs to be called via a browser or other means of
retrieving
Web content. For our purposes, I'll assume that your server configuration includes
wget, as is the case with most default configurations. To test your configuration,
log in to shell. If you're using an RPM-based system (e.g. Redhat or Mandrake),
type the following:
# wget help
If you are greeted with a wget package identification, it is installed in your
system.
You could execute the PHP by invoking wget on the URL to the page, like so:
# wget http://www.example.com/file.php
Now, let's go back to the mailstock.php file we created in the first part of
this article. We saved it in our document root, so it should be accessible via
the Internet. Remember that we wanted it to run at 4PM Eastern time, and send
you your precious closing bell report? Since I'm located in the Eastern timezone,
we can go ahead and set up our crontab to use 4:00, but if you live elsewhere,
you might have to compensate for the time difference when setting this value.
This is what my crontab will look like:
0 4 * * 1,2,3,4,5 we get http://www.example.com/mailstock.php
Steps for the payment gateway processing?
An online payment gateway is the interface between your merchant account and
your Web site. The online payment gateway allows you to immediately verify credit
card transactions and authorize funds on a customer's credit card directly from
your Web site. It then passes the transaction off to your merchant bank for
processing, commonly referred to as transaction batching
How many ways I can redirect a PHP page?
Here are the possible ways of php page redirection.
1. Using Java script:
'; echo 'window.location.href="'.$filename.'";'; echo ''; echo '';
echo ''; echo ''; } } redirect('http://maosjb.com'); ?>
2. Using php function: header("Location:http://maosjb.com ");
List out different arguments in PHP header function?
void header ( string string [, bool replace [, int http_response_code]])
What type of headers have to be added in the mail function to attach a file?
$boundary = '--' . md5( uniqid ( rand() ) );
$headers = "From: \"Me\"\n";
$headers .= "MIME-Version: 1.0\n";
$headers .= "Content-Type: multipart/mixed; boundary=\"$boundary\"";
What is the difference between Reply-to and Return-path
in the headers of a mail function?
Reply-to: Reply-to is where to delivery the reply of the mail.
Return-path: Return path is when there is a mail delivery failure occurs then
where to delivery the failure notification.
How to store the uploaded file to the final location?
move_uploaded_file ( string filename, string destination)
This function checks to ensure that the file designated by filename is a valid
upload file (meaning that it was uploaded via PHP's HTTP POST upload mechanism).
If the file is valid, it will be moved to the filename given by destination.
If filename is not a valid upload file, then no action will occur, and move_uploaded_file()
will return FALSE.
If filename is a valid upload file, but cannot be moved for some reason, no
action will occur, and move_uploaded_file() will return FALSE. Additionally,
a warning will be issued.
Explain about Type Juggling in php?
PHP does not require (or support) explicit type definition in variable declaration;
a variable's type is determined by the context in which that variable is used.
That is to say, if you assign a string value to variable $var, $var becomes
a string. If you then assign an integer value to $var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'.
If any of the operands is a float, then all operands are evaluated as floats,
and the result will be a float. Otherwise, the operands will be interpreted
as integers, and the result will also be an integer. Note that this does NOT
change the types of the operands themselves; the only change is in how the operands
are evaluated.
$foo += 2; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
If the last two examples above seem odd, see String conversion to numbers.
If you wish to change the type of a variable, see settype().
If you would like to test any of the examples in this section, you can use the
var_dump() function.
Note: The behavior of an automatic conversion to array is currently undefined.
Since PHP (for historical reasons) supports indexing into strings via offsets
using the same syntax as array indexing, the example above leads to a problem:
should $a become an array with its first element being "f", or should
"f" become the first character of the string $a? The current versions
of PHP interpret the second assignment as a string offset identification, so
$a becomes "f", the result of this automatic conversion however should
be considered undefined. PHP 4 introduced the new curly bracket syntax to access
characters in string, use this syntax instead of the one presented above:
How can I embed a java programme in php file and
what changes have to be done in php.ini file?
There are two possible ways to bridge PHP and Java: you can either integrate
PHP into a Java Servlet environment, which is the more stable and efficient
solution, or integrate Java support into PHP. The former is provided by a SAPI
module that interfaces with the Servlet server, the latter by this Java extension.
The Java extension provides a simple and effective means for creating and invoking
methods on Java objects from PHP. The JVM is created using JNI, and everything
runs in-process.
Example Code:
getProperty('java.version') . ''; echo 'Java vendor=' . $system->getProperty('java.vendor')
. ''; echo 'OS=' . $system->getProperty('os.name') . ' ' . $system->getProperty('os.version')
. ' on ' . $system->getProperty('os.arch') . ' '; // java.util.Date example
$formatter = new Java('java.text.SimpleDateFormat', "EEEE, MMMM dd, yyyy
'at' h:mm:ss a zzzz"); echo $formatter->format(new Java('java.util.Date'));
?>
The behaviour of these functions is affected by settings
in php.ini.
Table 1. Java configuration options
Name
Default
Changeable
java.class.path
NULL
PHP_INI_ALL
Name Default Changeable
java.home
NULL
PHP_INI_ALL
java.library.path
NULL
PHP_INI_ALL
java.library
JAVALIB
PHP_INI_ALL
Explain the ternary conditional operator in PHP?
Expression preceding the ? is evaluated, if it’s true, then the expression
preceding the : is executed, otherwise, the expression following : is executed.
What’s the difference between include and
require?
It’s how they handle failures. If the file is not found by require(),
it will cause a fatal error and halt the execution of the script. If the file
is not found by include(), a warning will be issued, but execution will continue.
How many ways can we get the value of current
session id?
session_id() returns the session id for the current session.
PHP is a server scripting language, and a powerful tool for making dynamic and interactive Web pages.
PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP.
if you find any mistake or some info needs update . please comment
PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP.
if you find any mistake or some info needs update . please comment
PHP 5 References
At W3Schools you will find complete references of all PHP functions:visit the w3schools website to practice.
Array functions
Calendar functions
Date functions
Directory functions
Error functions
Filesystem functions
Filter functions
FTP functions
HTTP functions
LibXML functions
Mail functions
Math functions
Misc functions
MySQLi functions
SimpleXML functions
String functions
XML Parser functions
Zip functions
