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PHP Interview Questions

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by Saikumar
Last modified: July 16th 2021

If you're looking for PHP Interview Questions for Experienced or Freshers, you are at the right place. There are a lot of opportunities from many reputed companies in the world. According to research PHP has a market share of about 79.23%. So, You still have the opportunity to move ahead in your career in PHP Development. Mindmajix offers Advanced PHP Interview Questions 2021 that helps you in cracking your interview & acquire a dream career as PHP Developer.

We have collected a bunch of PHP interview questions that are sourced from PHP experts. I hope these questions would help you in cracking the PHP interview and landing your dream job. If in case you have attended any PHP interview earlier and unable to find the same questions here, then feel free to comment on those questions in the comment section, and we will update them in this PHP interview questions blog so that it could help other students to learn from your experience.  Let's get into the QAs now.

Below mentioned are the Top Frequently asked PHP Interview Questions and Answers that will help you to prepare for the PHP interview. Let's have a look at them.

Types of PHP Interview Questions

Top 10 Frequently Asked PHP Interview Questions And Answers

  1. What is PHP?
  2. How to declare an array in PHP?
  3. What’s the difference between include and require?
  4. How to set cookies in PHP?
  5. What types of loops exist in PHP?
  6. How to redirect a page in PHP?
  7. What are the different types of errors in PHP?
  8. What is the use of the count() function in PHP?
  9. How to stop the execution of a PHP script?
  10. What is PEAR?

Let’s begin with the first Basic Level PHP interview questions.

Basic Level PHP Interview Questions

What are the basic differences between PHP, Python, and Ruby

PHP Vs Ruby Vs Python
PHP Ruby Python
To build dynamic web pages To make programming fun and flexible
Improve productivity and code readability
Version 7.2 Ruby 2.5.1 Python 3.6.4
Free Software Released Under PHP License Open Source and works on multiple platforms
Easy and quick to learn
Easy to learn Can be embedded into HTML
Runs in multiple systems and platforms
A great number of extensions and source codes A very high-level language
Readable and organized syntax
Provides extensive DB Support Can be easily connected to DB2, MySQL, Oracle, and Sybase
Not so effective in dealing with DB Connections

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 nontechnical person can create sites using its CMS. WordPress,osCommerce are the famous CMS of PHP. It is also an object-oriented programming language like java, C-sharp, etc. It is very easy for learning

Related Article: PHP Introduction And Variables, Operators In PHP

2. What is the use of “echo” in PHP?

It is used to print data in the webpage, Example: The following code print the text in the webpage

3. How to include a file on a PHP page?

We can include a file using the “include() ” or “require()” function with the 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.

Top 10 Programming Languages that you need to watch out to boost your career in 2021

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 the GET method but the POST method can transfer a large amount of data and POST is the secure method than GET method.

7. How to declare an array in PHP?

Ex: 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 parentheses with its argument list.

Example:

print(‘PHP Interview questions’);

print ‘Job Interview ‘);

9. What is the use of the in_array() function in PHP?

The in_array is used to check if a given value exists in an array or not.

Related Article: Cookies, Sessions, and Buffer In PHP

10. 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.

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11. 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 an 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. The session is mainly used for login/logout purposes while cookies using for user activity tracking

12. How to set cookies in PHP?

To set cookies in PHP,the setcookie() function is used. The setcookie() function needs to be called prior to any output generated by the script otherwise the cookie will not be sent.

Syntax: setcookie(“sample”, “ram”, time()+3600);

13. How to Retrieve a Cookie Value?

 The PHP syntax to Retrieve a Cookie Value is, 

Syntax: echo $_COOKIE[“user”];

Related Article: Headers, Downloading And File Uploading In PHP

14. How to create a session and set a value in session and how to Remove data from a session?

The PHP session_start() function is used to Create a new session.It als creates a new session ID for the user. session_start();

Create session Syntax : session_start();

To set a value in session, Session variables are set with the PHP global variable: $_SESSION.

Set value into session Syntax : $_SESSION[‘USER_ID’]=1;

Removing a specific value from a session is as simple as using the function unset(), just as you would for any other variable.

Remove data from a session Syntax : unset($_SESSION[‘USER_ID’];

15. What types of loops exist in PHP?

There are four types of loops that exist in PHP. They are

  1. for
  2. while
  3. do-while and
  4. foreach (NB: You should learn its usage)

16. How to create a MySQL connection?

The Syntax to create a MySQL connection is,

Syntax: mysql_connect(servername,username,password);

17. How to select a database?

The Syntax to select a database is,

Syntax: mysql_select_db($db_name);

These were some of the most commonly asked basic-level PHP interview questions. Let’s move on to the next advanced-level PHP interview questions.

Advanced level PHP Interview Questions

18. How to execute an SQL query? How to fetch its result?

The Syntax to  execute an SQL query is,

Syntax:

$my_qry = mysql_query(“SELECT * FROM `users` WHERE `u_id`=’1′; “);

$result = mysql_fetch_array($my_qry);

echo $result[‘First_name’];

19. Write a program using while loop

The PHP program using while loop is,

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

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

There are 4 ways to retrieve the data in the result set of MySQL using PHP:

mysql_fetch_row - Get a result row as an enumerated array
mysql_fetch_array - Fetch a result row as an associative array, a numeric array, or both
mysql_fetch_object - Fetch a result row as an object
mysql_fetch_assoc - Fetch a result row as an associative array

Related Article: Data Types In PHP

21. What is the use of explode() function?

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.

Syntax : array explode ( string $delimiter , string $string [, int $limit ] ); 

22. What is the difference between explode() and split() functions?

The split function splits the string into an array by regular expression. Explode splits a string into an array by string.

23. How to redirect a page in PHP?

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

24. How to stop the execution of a PHP script?

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

25. How to set a page as a home page on a PHP-based site?

index.php is the default name of the home page in PHP based sites

26. What is the difference between mysql_fetch_array() and mysql_fetch_assoc() ?

mysql_fetch_assoc function Fetch a result row as an associative array, Whilemysql_fetch_array() fetches an associative array, a numeric array, or both

27. What is the importance of the “method” attribute in an HTML form?

The “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 to 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.

28. What is the importance of the “action” attribute in an HTML form?

The action attribute determines where to send the form data in the form submission.

30. What is the use of the “enctype” attribute in an 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.

Related Article: Conditions And Loops In PHP

31. Define Object-Oriented Methodology

Object orientation is a software/Web development methodology that is based on modeling a real-world system. An object is the core concept involved in object orientation. An object is a copy of a real-world entity. An object-oriented model is a collection of objects and their inter-relationships.

32. How do you define a constant?

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

33. 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 does not close when the execution of your script ends. mysql_connect()provides only for the database new connection 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.

34. What is the use of “ksort” in PHP?

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

35. What is the difference between $var and $$var?

They are both variables. But $var is a variable with a fixed name. $$var is a variable whose name is stored in $var. For example, if $var contains “message”, $$var is the same as $message.

36. What are the different types of 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 shown 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 to 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 that does not exist or a non-existent function is called. These errors result in the termination of the script immediately and the default behavior of PHP is shown to them when they take place. Twelve different error types are used to represent these variations internally.

37. What is PEAR?

PEAR stands for "PHP Extension and Application Repository". 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.

38. Distinguish between urlencode and urldecode?

This method is best when encode a string to use in a query part of a URL. it returns a string in which all non-alphanumeric characters except -_. have replaced with a percentage(%) sign. the urldecode->Decodes URL to encode the string as any %and other symbols are decode by the use of the urldecode() function.

39. What is the use of the count() function in PHP?

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

About Author

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NameSaikumar
Author Bio

As a Senior Writer for Mindmajix, Saikumar has a great understanding of today’s data-driven environment, which includes key aspects such as Business Intelligence and data management. He manages the task of creating great content in the areas of Programming, Microsoft Power BI, Tableau, Oracle BI, Cognos, and Alteryx. Connect with him on LinkedIn and Twitter.