PHP Interview Question

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?


4.How can we get the browser properties using PHP?


echo $_SERVER[‘HTTP_USER_AGENT’].”\n\n”;

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?


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?


9. How can we create a database using php?


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(“”,”@”) will return “”.
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?


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?


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 retrieves them.

28. What is the difference between PHP and JavaScript?

javascript is a client side scripting language, so javascript can make popups and other things happens 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?

$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”;

36.What is PHP?

PHP: Hypertext Preprocessor is open source server-side scripting language that is widely used for web development. PHP scripts are executed on the server. PHP allows writing dynamically generated web pages efficiently and quickly. The syntax is mostly borrowed from C, Java and perl. PHP is free to download and use.

37. What is PEAR in php?

PEAR(PHP Extension and Application Repository) is a framework and repository for reusable PHP components. PEAR is a code repository containing all kinds of php code snippets and libraries.

PEAR also offers a command-line interface that can be used to automatically install “packages”.
Explain how to submit form without a submit button.

We can achieve the above task by using JavaScript code linked to an event trigger of any form field and call the document.form.submit() function in JavaScript code.

38.Echo vs. print statement.

echo() and print() are language constructs in PHP, both are used to output strings. The speed of both statements is almost the same.

echo() can take multiple expressions whereas print cannot take multiple expressions.

Print return true or false based on success or failure whereas echo doesn’t return true or false.

39. $message vs. $$message in PHP.

$message is a variable with a fixed name. $$message is a variable whose name is stored in $message.

If $message contains “var”, $$message is the same as $var.

40. Explain the different types of errors in PHP.

Notices, Warnings and Fatal errors are the types of errors in PHP


Notices represents non-critical errors, i.e. accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all but whenever required, you can change this default behavior.


Warnings are more serious errors but they do not result in script termination. i.e calling include() a file which does not exist. By default, these errors are displayed to the user.

Fatal errors:

Fatal errors are critical errors i.e. calling a non-existent function or class. These errors cause the immediate termination of the script.

41. Explain the importance of the function htmlentities.

The htmlentities() function converts characters to HTML entities.

42. What is MIME?

MIME – Multi-purpose Internet Mail Extensions.

MIME types represents a standard way of classifying file types over Internet.

Web servers and browsers have a list of MIME types, which facilitates files transfer of the same type in the same way, irrespective of operating system they are working in.

A MIME type has two parts: a type and a subtype. They are separated by a slash (/).

MIME type for Microsoft Word files is application and the subtype is msword, i.e. application/msword.

43. What is MVC?

Ans. MVC stands for Model, View, and Controller. PHP MVC is an effective way to manage the code into 3 different layers.

Model:  Model represents the information in application.

View: View represents the visual representation of information and data that you have entered in the application.

Controller: Controller is actually how and in which way you want to read the information in application.

44. What are the different types of CSS you can add in a page?

Ans. There are three types of CSS that can be added in a page.

1. External CSS.

2. Internal CSS.

3. Inline CSS.

45. Does PHP support multiple inheritances?

Ans. No, PHP support only single level of inheritance. A class can be inherited from a single class using keyword ‘extended’.

46. What is the difference between echo and print?

Ans. Initially both look same because both used to display any value. Main difference between echo and print is that echo is just used to display any string in output. It will display whatever is passed to it but on other hand print is a function itself it not only display any value but also can return value.

47. What is the difference between GET and POST method?

Ans. Whenever we fill any form on internet we can used one from two methods to send data on sever computer, that method can be either GET or POST. When we use the GET method all information is displayed on address bar. If can sent up to 1024 of data using GET method so it is good to use only when we are working with small scale applications and data is not that much sensitive. If we talk about POST method, No information will be displayed on address bar and we can send up to 2 mb of data using POST method. This limit can also extend further if required. PHP includes many CMS systems which can be used to handle the web content in a effective way.

48.What functions are used to get the image size, Width and Height?

Ans. getimagesize () to get the size of an image

Imagesx () to get width of an image

Imagesy () to get height of  an image.

49. How do you upload videos using PHP & MySQL?

We just need to copy the path of stored videos in the database rather than storing the videos files itself. All videos will be saved on a different folder and videos can be called from that folder when ever required. Default size is 2 mb for video files but we can change that size from max_file size option in php.ini file.

50. What are the different types of errors in PHP?

There are three types of errors encountered in PHP.

1. Notice: These are very normal and non-critical errors and they even not displayed to users. For examples accessing a variable that not existed at all.

2. Warning: These are little bit critical errors. These results are displayed to users but do not affect the output of code. For example trying to include any file that is not exists.

3. Fatal errors: These are really critical errors. For example calling any non existence class.

51. How constants are defined in a PHP script?

Define () is used to define constants in PHP.

define (“Newconstant”, 30);

52. How can we submit a form without using submit button?

We can use the hyper links to submit a form if we don’t want to use submit button. We have to use some java script code for that.

<a href=”javascript: document.myform.submit();”>Submit Me

53. 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

54. 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.

55. 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.

56. 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.

57. 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 .

58. How to declare an array in php?

Eg : var $arr = array(‘apple’, ‘grape’, ‘lemon’);

59. 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 ‘);

60. What is use of in_array() function in php ?

in_array used to checks if a value exists in an array

61. What is use of count() function in php ?

count() is used to count all elements in an array, or something in an object

62. 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.

63. 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

64. How to set cookies in PHP?

Setcookie(“sample”, “ram”, time()+3600);

65. How to Retrieve a Cookie Value?

eg : echo $_COOKIE[“user”];

66. 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’];

67. what types of loops exist in php?

for,while,do while and foreach (NB: You should learn its usage)

68. How to create a mysql connection?


69. How to select a database?


70. How to execute an sql query? How to fetch its result ?

$my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “);
$result = mysql_fetch_array($my_qry);
echo $result[‘First_name’];
Write a program using while loop

$my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “);
while($result = mysql_fetch_array($my_qry))
echo $result[‘First_name’.].”<br/>”;

71. How we can retrieve the data in the result set of MySQL using PHP?

1. mysql_fetch_row
2. mysql_fetch_array
3. mysql_fetch_object
4. mysql_fetch_assoc

72. 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.

73. 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.

74. 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
Write down the code for save an uploaded file in php.

if ($_FILES[“file”][“error”] == 0)
“upload/” . $_FILES[“file”][“name”]);
echo “Stored in: ” . “upload/” . $_FILES[“file”][“name”];

75. 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 test\n” );
fclose( $file );

76. 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.

77. 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.

78. How to redirect a page in php?

The following code can be used for it, header(“Location:index.php”);

79. How stop the execution of a php scrip ?

exit() function is used to stop the execution of a page

80. 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

81. How to find the length of a string?

strlen() function used to find the length of a string

82. 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.

83. what is the use of isset() in php?

This function is used to determine if a variable is set and is not NULL

84. 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

85. What is mean by an associative array?

Associative arrays are arrays that use string keys is called associative arrays.

86. 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.

87. 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.

88. 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

89. 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[]” />

90. 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

91. How do you define a constant?

Using define() directive, like define (“MYCONSTANT”,150)

92. 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);

93. 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.

94. 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.

95. What is the use of “ksort” in php?

It is used for sort an array by key in reverse order.

96. 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.

97. 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

98. 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.

99. How to delete a file from the system

Unlink() deletes the given file from the file system.

100. How to get the value of current session id?

session_id() function returns the session id for the current session.

101. 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, a numeric array, or both.
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
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.

102. 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.

103. what is sql injection ?

SQL injection is a malicious code injection technique.It exploiting SQL vulnerabilities in Web applications

104. What is x+ mode in fopen() used for?

Read/Write. Creates a new file. Returns FALSE and an error if file already exists

105. 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

106. 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.

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