Php interview questions

PHP interview questions and answers for freshers
Welcome !!!. In this section we are providing you some frequently asked PHP Interview
Questions which will help you to win interview session easily. Candidates must read this
section,Then by heart the questions and answers. Also, review sample answers and advice on
how to answer these typical interview questions. PHP is an important part of the web world, and
every web developer should have the basic knowledge in PHP.Common PHP interview
questions, which should help you become a best PHP codder. We hope you find these questions
useful. If you are an interviewer, Take the time to read the common interview questions you will
most likely be asked. Random
1. What is PHP?
PHP is a server side scripting language commonly used for web applications. PHP has
many frameworks and cms for creating websites.Even a non technical person can cretae
sites using its CMS.WordPress,osCommerce are the famus CMS of php.It is also an
object oriented programming language like java,C-sharp etc.It is very eazy for learning
2. What is the use of "echo" in php?
It is used to print a data in the webpage, Example: <?php echo 'Car insurance'; ?> , The
following code print the text in the webpage
3. How to include a file to a php page?
We can include a file using "include() " or "require()" function with file path as its
parameter.
4. What's the difference between include and require?
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.
5. require_once(), require(), include().What is difference between them?
require() includes and evaluates a specific file, while require_once() does that only if it
has not been included before (on the same page). So, require_once() is recommended to
use when you want to include a file where you have a lot of functions for example. This
way you make sure you don't include the file more times and you will not get the
"function re-declared" error.
6. Differences between GET and POST methods ?
We can send 1024 bytes using GET method but POST method can transfer large amount
of data and POST is the secure method than GET method .

7. How to declare an array in php?
Eg : var $arr = array('apple', 'grape', 'lemon');
8. What is the use of 'print' in php?
This is not actually a real function, It is a language construct. So you can use with out
parentheses with its argument list.
Example print('PHP Interview questions');
print 'Job Interview ');
9. What is use of in_array() function in php ?
in_array used to checks if a value exists in an array
10. What is use of count() function in php ?
count() is used to count all elements in an array, or something in an object
11. 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.
12. What is the difference between Session and Cookie?
The main difference between sessions and cookies is that sessions are stored on the
server, and cookies are stored on the user’s computers in the text file format. Cookies can
not hold multiple variables,But Session can hold multiple variables.We can set expiry for
a cookie,The session only remains active as long as the browser is open.Users do not
have access to the data you stored in Session,Since it is stored in the server.Session is
mainly used for login/logout purpose while cookies using for user activity tracking
13. How to set cookies in PHP?
Setcookie("sample", "ram", time()+3600);
14. How to Retrieve a Cookie Value?
eg : echo $_COOKIE["user"];
15. How to create a session? How to set a value in session ? How to Remove data from a
session?

Create session : session_start();
Set value into session : $_SESSION['USER_ID']=1;
Remove data from a session : unset($_SESSION['USER_ID'];
16. what types of loops exist in php?
for,while,do while and foreach (NB: You should learn its usage)
17. How to create a mysql connection?
mysql_connect(servername,username,password);
18. How to select a database?
mysql_select_db($db_name);
19. How to execute an sql query? How to fetch its result ?
$my_qry = mysql_query("SELECT * FROM ùsers` WHERE ù_id`='1'; ");
$result = mysql_fetch_array($my_qry);
echo $result['First_name'];
20. Write a program using while loop
$my_qry = mysql_query("SELECT * FROM ùsers` WHERE ù_id`='1'; ");
while($result = mysql_fetch_array($my_qry))
{
echo $result['First_name'.]."<br/>";
}
21. How we can retrieve the data in the result set of MySQL using PHP?
o 1. mysql_fetch_row
o 2. mysql_fetch_array
o 3. mysql_fetch_object
o 4. mysql_fetch_assoc
22. What is the use of explode() function ?
Syntax : array explode ( string $delimiter , string $string [, int $limit ] );
This function breaks a string into an array. Each of the array elements is a substring of
string formed by splitting it on boundaries formed by the string delimiter.
23. What is the difference between explode() and split() functions?
Split function splits string into array by regular expression. Explode splits a string into
array by string.

24. What is the use of mysql_real_escape_string() function?
It is used to escapes special characters in a string for use in an SQL statement
25. Write down the code for save an uploaded file in php.
if ($_FILES["file"]["error"] == 0)
{
move_uploaded_file($_FILES["file"]["tmp_name"],
"upload/" . $_FILES["file"]["name"]);
echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
}
26. How to create a text file in php?
$filename = "/home/user/guest/newfile.txt";
$file = fopen( $filename, "w" );
if( $file == false )
{
echo ( "Error in opening new file" ); exit();
}
fwrite( $file, "This is a simple testn" );
fclose( $file );
27. How to strip whitespace (or other characters) from the beginning and end of a
string ?
The trim() function removes whitespaces or other predefined characters from both sides
of a string.
28. What is the use of header() function in php ?
The header() function sends a raw HTTP header to a client browser.Remember that this
function must be called before sending the actual out put.For example, You do not print
any HTML element before using this function.
29. How to redirect a page in php?
The following code can be used for it, header("Location:index.php");
30. How stop the execution of a php scrip ?
exit() function is used to stop the execution of a page
31. How to set a page as a home page in a php based site ?

index.php is the default name of the home page in php based sites
32. How to find the length of a string?
strlen() function used to find the length of a string
33. what is the use of rand() in php?
It is used to generate random numbers.If called without the arguments it returns a pseudo-random
integer between 0 and getrandmax(). If you want a random number between 6
and 12 (inclusive), for example, use rand(6, 12).This function does not generate
cryptographically safe values, and should not be used for cryptographic uses. If you want
a cryptographically secure value, consider using openssl_random_pseudo_bytes()
instead.
34. what is the use of isset() in php?
This function is used to determine if a variable is set and is not NULL
35. What is the difference between mysql_fetch_array() and mysql_fetch_assoc() ?
mysql_fetch_assoc function Fetch a result row as an associative array, While
mysql_fetch_array() fetches an associative array, a numeric array, or both
36. What is mean by an associative array?
Associative arrays are arrays that use string keys is called associative arrays.
37. What is the importance of "method" attribute in a html form?
"method" attribute determines how to send the form-data into the server.There are two
methods, get and post. The default method is get.This sends the form information by
appending it on the URL.Information sent from a form with the POST method is invisible
to others and has no limits on the amount of information to send.
38. What is the importance of "action" attribute in a html form?
The action attribute determines where to send the form-data in the form submission.
39. What is the use of "enctype" attribute in a html form?
The enctype attribute determines how the form-data should be encoded when submitting
it to the server. We need to set enctype as "multipart/form-data" when we are using a
form for uploading files
40. How to create an array of a group of items inside an HTML form ?

We can create input fields with same name for "name" attribute with squire bracket at the
end of the name of the name attribute, It passes data as an array to PHP.
For instance :
<input name="MyArray[]" /> <input name="MyArray[]" /> <input
name="MyArray[]" /> <input name="MyArray[]" />
41. Define Object-Oriented Methodology
Object orientation is a software/Web development methodology that is based on the
modeling a real world system.An object is the core concept involved in the object
orientation. An object is the copy of the real world enity.An object oriented model is a
collection of objects and its inter-relationships
42. How do you define a constant?
Using define() directive, like define ("MYCONSTANT",150)
43. How send email using php?
To send email using PHP, you use the mail() function.This mail() function accepts 5
parameters as follows (the last 2 are optional). You need webserver, you can't send email
from localhost. eg : mail($to,$subject,$message,$headers);
44. How to find current date and time?
The date() function provides you with a means of retrieving the current date and time,
applying the format integer parameters indicated in your script to the timestamp provided
or the current local time if no timestamp is given. In simplified terms, passing a time
parameter is optional - if you don't, the current timestamp will be used.
45. Difference between mysql_connect and mysql_pconnect?
There is a good page in the php manual on the subject, in short mysql_pconnect() makes
a persistent connection to the database which means a SQL link that do not close when
the execution of your script ends. mysql_connect()provides only for the
databasenewconnection while using mysql_pconnect , the function would first try to find
a (persistent) link that's already open with the same host, username and password. If one
is found, an identifier for it will be returned instead of opening a new connection... the
connection to the SQL server will not be closed when the execution of the script ends.
Instead, the link will remain open for future use.
46. What is the use of "ksort" in php?
It is used for sort an array by key in reverse order.
47. What is the difference between $var and $$var?

They are both variables. But $var is a variable with a fixed name. $$var is a variable
who's name is stored in $var. For example, if $var contains "message", $$var is the same
as $message.
48. What are the encryption techniques in PHP
MD5 PHP implements the MD5 hash algorithm using the md5 function,
eg : $encrypted_text = md5 ($msg);
mcrypt_encrypt :- string mcrypt_encrypt ( string $cipher , string $key , string $data ,
string $mode [, string $iv ] );
Encrypts plaintext with given parameters
49. What is the use 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.
50. How to delete a file from the system
Unlink() deletes the given file from the file system.
51. How to get the value of current session id?
session_id() function returns the session id for the current session.
52. What are the differences between mysql_fetch_array(), mysql_fetch_object(),
mysql_fetch_row()?
o Mysql_fetch_array Fetch a result row as an associative array, a numeric array, or
both.
o mysql_fetch_object ( resource result ) 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
o 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.
53. What are the different types of errors in PHP ?
Here are three basic types of runtime errors in PHP:
o 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.

o 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.
o 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.
54. what is sql injection ?
SQL injection is a malicious code injection technique.It exploiting SQL vulnerabilities in
Web applications
55. What is x+ mode in fopen() used for?
Read/Write. Creates a new file. Returns FALSE and an error if file already exists
56. How to find the position of the first occurrence of a substring in a string
strpos() is used to find the position of the first occurrence of a substring in a string
57. What is PEAR?
PEAR is a framework and distribution system for reusable PHP components.The project
seeks to provide a structured library of code, maintain a system for distributing code and
for managing code packages, and promote a standard coding style.PEAR is broken into
three classes: PEAR Core Components, PEAR Packages, and PECL Packages. The Core
Components include the base classes of PEAR and PEAR_Error, along with database,
HTTP, logging, and e-mailing functions. The PEAR Packages include functionality
providing for authentication, networking, and file system features, as well as tools for
working with XML and HTML templates.
58. Distinguish between urlencode and urldecode?
This method is best when encode a string to used in a query part of a url. it returns a
string in which all non-alphanumeric characters except -_. have replece with a
percentege(%) sign . the urldecode->Decodes url to encode string as any %and other
symbole are decode by the use of the urldecode() function.
59. What are the different errors in PHP?
In PHP, there are three types of runtime errors, they are:
Warnings:
These are important errors. Example: When we try to include () file which is not
available. These errors are showed to the user by default but they will not result in ending
the script.

Notices:
These errors are non-critical and trivial errors that come across while executing the script
in PHP. Example: trying to gain access the variable which is not defined. These errors are
not showed to the users by default even if the default behavior is changed.
Fatal errors:
These are critical errors. Example: instantiating an object of a class which does not exist
or a non-existent function is called. These errors results in termination of the script
immediately and default behavior of PHP is shown to them when they take place. Twelve
different error types are used to represent these variations internally.
1. Who is the father of PHP ?
Rasmus Lerdorf is known as the father of PHP.
2. What is the difference between $name and $$name?
$name is variable where as $$name is reference variable like $name=sonia and $$name=singh so $sonia value is singh.
3. What are the method available in form submitting?
GET and POST
4.How can we get the browser properties using PHP?
<?php
echo $_SERVER[‘HTTP_USER_AGENT’].”nn”;
$browser=get_browser(null,true);
print_r($browser);
?>
5. 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. Sessions
are commonly used to store temporary data to allow multiple PHP pages to offer a complete functional transaction for the same
visitor.
6. How can we register the variables into a session?
<?php
session_register($ur_session_var);
?>
7. How many ways we can pass the variable through the navigation between the pages?
Register the variable into the session
Pass the variable as a cookie
Pass the variable as part of the URL
8. How can we know the total number of elements of Array?
sizeof($array_var)
count($array_var)
9. How can we create a database using php?
mysql_create_db();
10. 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.
11. What are encryption functions in PHP?
CRYPT(), MD5()
12. How to store the uploaded file to the final location?
move_uploaded_file( string filename, string destination)

13. Explain mysql_error().
The mysql_error() message will tell us what was wrong with our query, similar to the message we would receive at the MySQL
console.
14. What is Constructors and Destructors?
CONSTRUCTOR : PHP allows developers to declare constructor methods for classes. Classes which have a constructor method
call this method on each newly-created object, so it is suitable for any initialization that the object may need before it is used.
DESTRUCTORS : PHP 5 introduces a destructor concept similar to that of other object -oriented languages, such as C++. The
destructor method will be called as soon as all references to a particular object are removed or when the object is explicitly
destroyed or in any order in shutdown sequence.
15. Explain the visibility of the property or method.
The visibility of a property or method must be defined by prefixing the declaration with the keywords public, protected or
private.
Class members declared public can be accessed everywhere.
Members declared protected can be accessed only within the class itself and by inherited and parent classes.
Members declared as private may only be accessed by the class that defines the member.
16. What are the differences between Get and post methods.
There are some defference between GET and POST method
1. GET Method have some limit like only 2Kb data able to send for request
But in POST method unlimited data can we send
2. when we use GET method requested data show in url but
Not in POST method so POST method is good for send sensetive request
17. What are the differences between require and include?
Both include and require used to include a file but when included file not found
Include send Warning where as Require send Fatal Error
18. What is use of header() function in php ?
The header() function sends a raw HTTP header to a client.We can use herder()
function for redirection of pages. It is important to notice that header() must
be called before any actual output is seen.
19. List out the predefined classes in PHP?

Directory
stdClass
__PHP_Incomplete_Class
exception
php_user_filter
20. 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'.
21. How can we encrypt the username and password using php?
You can encrypt a password with the following Mysql>SET PASSWORD=PASSWORD("Password");
We can encode data using base64_encode($string) and can decode using base64_decode($string);
22. What is the difference between explode and split?
Split function splits string into array by regular expression. Explode splits a string into array by string.
For Example:explode(" and", "India and Pakistan and Srilanka");
split(" :", "India : Pakistan : Srilanka");
Both of these functions will return an array that contains India, Pakistan, and Srilanka.
23. How do you define a constant?
Constants in PHP are defined using define() directive, like define("MYCONSTANT", 100);
24. How do you pass a variable by value in PHP?
Just like in C++, put an ampersand in front of it, like $a = &$b;
25. What does a special set of tags <?= and ?> do in PHP?
The output is displayed directly to the browser.
26. How do you call a constructor for a parent class?
parent::constructor($value)
27. What’s the special meaning of __sleep and __wakeup?
__sleep returns the array of all the variables than need to be saved, while __wakeup ret rieves them.
28. What is the difference between PHP and JavaScript?

javascrip t is a client side scrip ting language, so javascrip t can make p op up s and other things hap p ens on someone’s PC. While
PHP is server side scripting language so it does every stuff with the server.
29. What is the difference between the functions unlink and unset?
unlink() deletes the given file from the file system.
unset() makes a variable undefined.
30. How many ways can we get the value of current session id?
session_id() returns the session id for the current session.
31. What are default session time and path?
default session time in PHP is 1440 seconds or 24 minutes
Default session save path id temporary folder /tmp
32. for image work which library?
we will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other
libraries, depending on which image formats you want to work with.
33. How can we get second of the current time using date function?
<?php
$second = date(“s”);
?>
34. What are the Formatting and Printing Strings available in PHP?
printf()- Displays a formatted string
sprintf()-Saves a formatted string in a variable
fprintf() -Prints a formatted string to a file
number_format()-Formats numbers as strings
35. How can we find the number of rows in a result set using PHP?
$result = mysql_query($sql, $db_link);
$num_rows = mysql_num_rows($result);
echo "$num_rows rows found";
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