PHP Interview Questions?

In recent years, the web development field has been rapidly expanding due to the widespread shift to digital solutions. Whether it's creating online stores or interactive websites, PHP plays a crucial role in making websites that work well and can adapt to various needs.

The need for PHP developers is growing in India and worldwide. Not just large companies, but also web development firms from all over the world are recruiting talented PHP developers.

PHP developers in India can earn a good income because there aren't enough skilled developers to meet the demand. If you take a hands-on web development course or PHP training, you can quickly kickstart your career in this field.

Before you apply for a job, it's essential to familiarize yourself with commonly asked PHP interview questions and their answers. This preparation will increase your chances of succeeding in the interview and landing your ideal job with your preferred company. In this detailed guide, we've compiled a set of questions that cover various aspects of PHP. These questions will assist you in preparing for your job interview effectively and comprehensively if you're a PHP developer.

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Introduction to PHP Programming Language

PHP is a scripting language used for creating dynamic websites and mobile APIs. It can handle databases like MySQL and is often mixed with HTML. PHP is great for managing server sessions, handling changing content, and working with databases. It's perfect for building websites, like e-commerce sites, and is supported by most web hosting servers.

Basic PHP Interview Questions & Answers

Review these PHP interview questions and answers for both beginners and experienced candidates to increase your chances of landing a PHP developer job. These questions are crafted to match what employers commonly ask during the hiring process. 

1. What is PHP?

PHP stands for PHP Hypertext Preprocessor. It is a scripting language that is used for web development. It is an open-source language that is embedded into HTML. When a server executes the code, then the client gets a generated HTML.

2. Who is PHP Developer?

A PHP developer is a programmer who writes code at the server-side for web application logic. These programmers generally develop components that are supported at the back-end.

These developers connect the application with third-party web services and integrate the codes with the application to support the front-end web application logic.

3. Where is PHP used?

PHP is used on all the widely used operating systems like Windows, macOS, Linux, etc. PHP has support for web servers that are available in the market.

The dynamic web page content is generated with this. It is mainly used for web development. Developers prefer to use this language to build server-side webpages and applications.

4. Who developed PHP?

PHP was created by Rasmus Lerdorf, a Danish-Canadian developer, in 1994. All the new versions are produced by the PHP Group.

5. Name some big brands or top websites that use PHP.

Big names like Etsy, Facebook, Pinterest, Tumblr, WordPress, Wikipedia, etc. are using PHP as the back-end language.

6. What is PEAR in PHP?

PEAR in PHP stands for PHP Extension and Application Repository. It is a repository and framework that is used for reusing the PHP components. PEAR enables the upgraded level of programming. It has various PHP libraries and code snippets. Moreover, it also contains a command-line interface for installing packages in PHP.

7. What are traits in PHP?

PHP traits are like reusable sets of code that can be used in different parts of a program. They're handy in languages that can't do multiple inheritances, and they help work around the limitations of inheritance in a program.

8. What are the disadvantages of PHP?

PHP is often not preferred for large content-focused web applications because it's considered less secure due to the widespread availability of its source code (open source). Additionally, the various features and tools in PHP can negatively impact the performance of applications. PHP is also criticized for its average ability to handle errors effectively.

9. Name some PHP-based CMS platforms.

WordPress, Joomla, Magento, and Drupal are some of the top Content Management Systems developed in PHP programming.

10. What is a final class in PHP?

It is used when an immutable class like a string class is created. In PHP, classes and methods can be declared final, but properties can not be declared final. A final keyword indicates that the method can not be overridden by subclasses.

11. What is the difference between unlink() and unset() functions in PHP?

The unlink() function is used for handling the file system. It deletes the file that is given as an entry. Whereas, the unset() function is used for managing variables. It makes a variable undefined.

12. What is the meaning of the PHP array operator ‘===’?

When both the sides have the same values or keys in the same order and have the same type, this type of operator is used.

13. Is PHP case-sensitive?

PHP is a partial case-sensitive language. The variables in PHP are case-sensitive, and functions are not case-sensitive. User-defined functions in PHP are also not case-sensitive.

14. What are print and echo in PHP language?

The echo in PHP can output one or more strings, and print can output only one. The echo is faster, and the print is slower.

15. How to set up a new database with PHP and MySQL?

A script is used to form a connection to the MySQL server. After verification of connection, it is checked by writing an example query. The queries are saved in a string variable, and then the constructed queries run.

16. How to find that a given variable is empty in PHP?

The empty() function is used to check if a variable in a program has any value or not.

17. What is MIME in PHP?

MIME (Multipurpose Internet Mail Extensions) in PHP is a standard used for identifying the type of data in a web response or email attachment. It helps define the format of data, enabling proper handling and rendering of content, such as images (image/jpeg), text (text/html), or multimedia (audio/mpeg).

18. What is the main update in PHP 5 that was not in PHP 4?

The main update in PHP 5, not present in PHP 4, was the introduction of object-oriented programming (OOP) features. PHP 5 added support for classes and improved memory management, making it easier to create more organized and efficient code using OOP principles.

19. What is the difference between PHP constants and variables?

Variables in PHP can change their values during the program, while constants stay constant and don't change. Variables use a dollar sign ($), like $name, and their values can vary. Constants are defined using "define" and stay the same throughout the script, like define("PI", 3.14). So, variables can change, but constants remain fixed.

20. What is the relationship between HTML and PHP?

HTML and PHP work together to create dynamic web pages. HTML is used for structuring the content and layout of a web page, while PHP is a server-side scripting language that helps make web pages interactive by generating dynamic content. PHP can embed within HTML to create powerful, data-driven websites.

21. What are errors in PHP?

Errors in PHP are of 4 types.

  • Notices: These errors occur when a script is executed.
  • Warnings: Execution of the script is not interrupted by this, and it can be viewed by default.
  • Syntax of parsing error: When a semicolon, quote mark, or parenthesis is missing in a program, this error takes place.
  • Fatal: It happens when the execution of the script is terminated.

22. Why is the use of foreach loop in PHP?

A "foreach" loop in PHP is used to go through each item in a list (like an array) and perform actions on each item one by one.

23. What is include() function in PHP?

The include() function is used to copy the content of a file called in the function. When the file can’t be found, it produces a warning.

24. What is require() function in PHP?

The require() function works same as include() function. It takes the file and copies the data into a file. When the file can’t be found, it produces a fatal error.

25.Explain session_start() function and session_destroy() function in PHP?

session_start() is a PHP function used to begin or resume a user's session, which allows you to store data across multiple web pages. It creates a unique session ID for each user and initializes a storage area for session data.

session_destroy() is used to end a session, making all the stored session data inaccessible. It's like logging out, clearing all the session information, and preventing any further data from being saved in the session.

26. Which operator is used to concatenate two strings in PHP?

In PHP, you can concatenate (join together) two strings using the period (.) operator.

For example, if you have two strings, "Hello" and " world," you can concatenate them like this: "Hello" . " world." This will result in the string "Hello world."

The period (.) operator is used to combine text or characters from multiple strings into a single string, making it useful for building longer text or messages in PHP.

27. What is overriding and overloading in PHP?

Overriding is pertinent to derived classes in PHP. When a parent class defines a method and the derived class needs to override that particular method, the concept of overriding takes place.

When functions have similar signatures but different parameters, the concept of defining functions takes place. This process is called overloading in PHP.

28. What is the command line for executing a PHP script?

PHP Command Line Interface (CLI) is used to execute a PHP script. The command used for script execution is:

PHP script.php

29. What are image functions in PHP?

GD library is used to execute PHP image functions. The imagetypes() is also used to find out the image type and format that is also supported by the latest version of GD-PHP.

30. What are __wakeup and __sleep methods in PHP?

The __wakeup method in PHP is used to retrieve the array of all the variables.

On the other hand, the __sleep method is used to return the array of all the variables. These both are used for functions that are needed for saving the arrays.

31. How to find the number of rows that are returned in a result set and the number of entries affected by a query in PHP?

We can use the mysqli_affected_rows() function to return the total number of entries affected by an SQL query in PHP.

32. What are the different types of arrays in PHP?

The array is of three types in PHP:

  • Indexed array:It basically is an array with a numeric key. Values in an indexed array are stored in a linear order.
  • Associative array:It is an array with strings for indexing elements. Values of elements are stored in association with key values.
  • Multidimensional array:It is an array with multiple arrays within itself. Values are accessed with the help of multiple indices.

33. What are some popular PHP frameworks?

These are some of the most used PHP frameworks:

  • Laravel
  • Symfony
  • CodeIgniter
  • Zend Framework (Laminas):
  • Yii 2
  • Phalcon
  • Slim
  • CakePHP

34. What is the basic role of the parser in PHP?

It is a library that is used to create the syntax tree of a source code. For this, the parser first passes the source code through a lexical analyzer, and then the syntax tree is formed.

The benefit of using a PHP parser is that it helps in analyzing static code. Programmers or web developers can check the code for syntax errors and meet quality criteria.

Advanced PHP Interview Questions for Experienced (Senior Developer)

If you're familiar with PHP and have been working as a developer for a few years, you can use these PHP interview questions and answers for experienced professionals to assess your deep understanding of the language.

1. What is PDO in PHP?

PDO stands for PHP Data Object. It is a PHP extension with a core PDO class and drivers that are database specific. PDO drivers can be accessed with the help of the PDO extension.

PHP PDO has a data-access abstraction layer. The function issues queries and fetches data without focusing on the database.

2. What is Path Traversal in PHP?

It is an attack to read the files of a web application. This attack is also called a dot-dot-slash (../) attack to climb to a higher-level directory. Path traversal in PHP is done to gain access to passwords and other sensitive information stored.

3. What do you understand by cURL in PHP?

It is a library in PHP that is used for making HTTP requests from the server. The Client URL or cURL allows users to connect to a URL and retrieve data from the HTML page, header, and other data.

4. What is the difference between $message and $$message in PHP?

$message is a regular variable, and data stored in this is fixed.

Whereas, $$message is a reference variable, and data stored can be changed dynamically.

$message has a fixed name, and the value stores a fixed value, but $$message stores variable data.

5.How to execute PHP with Apache/ Nginx?

Web servers are not designed to understand and parse PHP files. There are additional programs that are used to do that.

Here are some ways to execute PHP with Apache/ Nginx:

  • Mod_php: It means to use PHP as an Apache module.
  • FastCGI: It is a PHP process that interprets PHP code and not Apache.
  • PHP-FRM: It is an alternative FastCGI Process Manager (FPM), which is used on sites with heavy traffic.

6. What are php.ini and .htaccess files in PHP?

These files are used to make changes in PHP settings.

  • php.ini file: When PHP runs as CGI, these files are used. These files can be used as default settings or editing a PHP file.
  • .htaccess file:These files are used to change or manage the overall behavior of a site.

    These files work when PHP is installed as Apache Module. A site can redirect a domain’s page to one page to HTTP or www.

7. What is type juggling in PHP?

When the type of the variable is changed on the basis of the assigned value, it is called type juggling in PHP.

8. How to make cookies in PHP?

The cookie is a small piece of information stored in the client browser used to recognize the user. When a client requests to the server on a site, the cookie is embedded with the request in PHP.

The setcookie() function is used to make cookies in PHP. This function is called before any script output generation in PHP.

9.What is Smarty in PHP?

It is a template engine that is written in PHP. Smarty will include variables and operators to allow adaptability in the particular templates. In PHP, Smarty is used to separate the concerns. It simplifies the program, which allows the front-end to change from its back-end.

10. What is the role of the lambda function used in PHP?

A lambda function is used to store the data into the variables and then pass that data to arguments for the usage in various other functions and methods. This is also used to store data into variables. A user can see it as per the demand without defining it one more time.

11. How would you display the output of a program directly in the browser?

Special tags <?= and ?> are used to display output directly to the browser.

12. What is hashing password in PHP?

It is a method in PHP to transform a single password into a string with a hashed password. This process can only be done one way, and the hashed passwords can not be moved to the original ones.

Hashing of passwords is done to improve the security of the program and the system. Some of the most used hashing algorithms in PHP are md5, bcrypt, sha1, and crypt.

13. What is Mbstring in PHP?

It is an extension that is used to handle strings that are non-ASCII. It provides multibyte-specific string functions used for multibyte encoding. If there are more than 256 characters present in a byte-wise coding system, multibyte character encoding schemes are used.

Mbstring handles encoding based on Unicode like UCS2 and UTF8. It is used to handle character encoding conversion between encoding pairs. Moreover, it has an overloading feature to add multibyte to string functions. It also provides multibyte-specific string functions that detect the beginning or ending of the multibyte characters.

14. What are ksort() and usort() functions in PHP?

Both the functions are used to sort associative arrays in PHP.

  • ksort(): It is a function that is used to sort arrays according to key values.
  • asort(): It is a function that is used to sort arrays according to their values.

15. What are GET and POST in PHP?

  • GET: It is used to display the data submitted as a part of the URL, and it allows only ASCII data. It can handle up to 2048 characters and is used to retrieve data.
  • POST: The information is not shown as per the request in the POST. It has no such request as a character limit, and binary data is also allowed in this. It is used to insert and update the data in PHP.

16. What is type hinting in PHP?

The type hinting was introduced in PHP 5. It is used to specify the data type for function declaration in PHP like arrays, objects, etc.

When the function is not of a specified type, the run time will show an error, and the program will not be able to execute. It is used to organize the code better.

17. How to export data into Excel files in PHP?

With the help of a .csv file and using a separator between fields, data can be exported into Excel files in PHP.

18. What things would you consider before naming a variable in PHP?

Here are some of the rules you must follow before naming variables in PHP:

  • A variable in PHP must start with a $.
  • A variable in PHP must end with the name of the variable.
  • The first characters of the variable must be an underscore or a letter.
  • Variables are case-sensitive in PHP.
  • A variable name can have letters, digits, and underscores.
  • Special characters and spaces are not allowed.

OOPS in PHP Interview Questions

The concept of OOPS is used in PHP language, and here are some of the commonly asked object-oriented programming PHP interview questions for you. You can prepare with these questions as these are the most asked questions on the concept of OOPS.

1. What is OOPS in PHP?

When functions are used to perform operations in a program, it is called procedural PHP programming language. When objects are created with data and functions, it is called OOPS in PHP.

2. What is a class in PHP OOPs?

A class in OOPS decides the behavior of an object, as well as what an object can contain. Using the class, the programmers can create specific objects.

The class is declared using the class keyword, along with the class name and curly braces.

Top Companies Hiring PHP Developers in India

The demand is on the rise for PHP developers as it is one of the most used languages. The regular updates in PHP are the main reason it won’t go out of demand.

If you are looking to build a career in PHP development, here is the list of top companies that are hiring PHP programmers and developers in India.

  • Tata Consultancy Services (TCS)
  • Infosys
  • Wipro
  • HCL Technologies
  • Tech Mahindra
  • Cognizant
  • Accenture
  • Capgemini
  • IBM India
  • Deloitte
  • Amazon India
  • Flipkart
  • Paytm
  • Zoho Corporation
  • Mindtree
  • Larsen & Toubro Infotech (LTI)
  • Adobe India
  • Oracle India
  • Microsoft India
  • SAP Labs India

What is the Average PHP Developer Salary in India?

The average salary of a PHP Developer in India is INR 2.88 LPA. With experience and level of skills, the salary increases.

The salary of a PHP developer also depends on the company location. For instance, companies in Bangalore, Pune, Chennai, Mumbai, etc. offer higher packages compared to tier II and tier III cities.

In terms of career growth, this is a great field because the demand is increasing for this skill. You can also choose to become a freelance developer to get high-paying international projects.

PHP Related to Interview Questions FAQs

Here are some of the most asked questions that are generally asked regarding PHP. It will clear your queries related to the PHP programming career.

The scope of PHP is very good as almost 80% of the websites use PHP as a development language. It is a decent career with constant growth that will land you in a pool full of opportunities as a developer.

Yes, PHP is still in demand, and it is not going out of demand anytime soon. The regular updates in PHP are one of the main reasons it will stay relevant in the near future as well in the sector of development.

You can purchase a PHP course from Arfi Technology and work on your skills. After the skill development, you can take the help of these interview questions to prepare for the interview. You can start a decent career in development in PHP after cracking the interview.

Here are some of the top skills that are required to become a PHP developer:

  • Knowledge of Ajax, MySQL, and jQuery
  • Framework of CakePHP
  • Knowledge of APIs and Linux/ UNIX
  • Knowledge of MVC framework architecture

If you are working on becoming a full-stack developer, then knowledge of CSS, HTML, and JavaScript is also needed.

PHP is used to create dynamic content and interact with databases in a website. It is known for the simplicity of the code, flexibility, speed, etc.

It is not a tough language to learn. You can learn this language with ease if you know the basics of programming. Purchase an online course and learn complete PHP.

You can learn PHP in three to 8 months. It completely depends on the commitment. You can learn PHP from a course from Arfi Technology in 7 months.