PHP Interview Questions and Answers -2026

PHP is a popular server-side scripting language, widely known for its efficiency in web development and versatility across various platforms. PHP is extensively utilized by top companies such as Facebook, WordPress, Slack, Wikipedia, MailChimp, and many more due to its robust features and high performance.

In this article, we will provide the Top 60+ PHP Interview Questions 2025 designed for both freshers and experienced professionals with 3, 5, and 8 years of experience. Here, we cover everything, including core PHP concepts, Object-Oriented Programming (OOP), error handling, security practices, PHP frameworks, database interactions, and more.

PHP Interview Questions for Beginners

1. What is PHP?

PHP is a general-purpose programming language used to design a website or web application. It is a server-side scripting language embedded with HTML to develop a Static website, a Dynamic website, and a Web application. It was created by Rasmus Lerdorf in 1994.

• Server-Side Language: PHP runs on the server, generating HTML or other content,Destroys which is then sent to the client’s browser.
• Dynamic Content Creation: PHP can interact with databases and process user input, making websites interactive and data-driven.
• Cross-Platform: It works on various platforms, including Windows, Linux, and macOS.
• Integration with Databases: PHP easily connects with databases like MySQL, making it ideal for building dynamic, database-driven websites.
• Open-Source: PHP is free to use, with a large community of developers contributing to its ecosystem.

2. How do you redirect a page in PHP?

In PHP, you can redirect a user to a different page using the header() function. This function sends a raw HTTP header to the browser, telling it to navigate to a different URL.

header("Location: newpage.php");
exit();

3. What is the difference between session_unset() and session_destroy()?

Both session_unset() and session_destroy() are used to manage session data in PHP, but they serve different purposes:

4. Is PHP a case-sensitive language?

Yes, PHP is a case-sensitive language for variables, but function names, class names, and constants are not case-sensitive.

5. What is the difference between PHP and ASP.NET?

6. How does PHP handle form data?

PHP handles form data through two main superglobals: $_GET and $_POST.

• $_GET is used to collect form data sent through the URL (typically from a query string). It’s often used for search forms or when the data should be visible in the URL.
• $_POST is used to collect form data sent via HTTP POST, which is more secure as the data is not visible in the URL. It’s typically used for sensitive data like login credentials or when submitting large amounts of data.

7. What is the full form of PHP?

PHP is the abbreviation of Hypertext Preprocessor, the following and earlier it was abbreviated as Personal Home Page.

8. What was the old name of PHP?

The old name of PHP was Personal Home Page.

9. What are the uses of PHP?

PHP is widely used for various tasks in web development. Some of its key uses include the following and:

• It is a server-side scripting language used to design dynamic websites or web applications.
• It receives data from forms to generate the dynamic page content.
• It can work with databases and sessions, send and receive cookies, send emails, etc.
• It can be used to add, delete, and modify content within the database.
• It can be used to set arerestriction to the user to access the web page.

10. What is PEAR in PHP?

PEAR(PHP Extension and Application Repository) is a framework and distribution system for reusable PHP components. It stands for PHP Extension and Application Repository. It contains PHP snippets and a library to reuse the code. It provides a command-line interface to install packages.

Some of the key features of PEAR

• Reusable Code
• Package Management
• Standardization
• Autoloading
• Command-line Interface (CLI)
• Web-based Interface

11. What is the difference between static and dynamic websites?

Static Website: Content is fixed and doesn’t change unless manually updated by the developer. Static Websites areIt may built using HTML, CSS, and JavaScript; each page is a separate file.

• Limited customization for the user; all visitors see the same content.
• Faster load times since the content is already pre-built and served as-is.
• Easier to maintain; updating content requires manual edits to individual pages.
• Generally cheaper to build and host.

Dynamic Website: Content is generated in real-time, often based on user interaction or database queries. Built using server-side technologies like PHP, ASP.NET, or Node.js, and may use databases to retrieve content.

• Content can change based on user input or preferences (e.g., login systems, product catalogs).
• May have slower load times due to real-time content generation and database queries.
• Requires backend management and database updates, which can be more complex.
• It mayneed be more expensive due to the need for server-side scripting and database support.

12. What are the rules for naming a PHP variable?

The following two rules need to be followed while naming a PHP variable.

• A variable in PHP must start with a dollar sign ($), followed by the variable name. For example, $price = 100; where price is the variable name.
• Variable names must begin with a letter (a-z, A-Z) or an underscore (_).
• A variable name can consist of letters, numbers, or underscores, but special characters like +, -, %, &, etc., are not allowed.
• PHP variable names cannot contain spaces.
• PHP variables are case-sensitive, meaning $NAME and $name are considered different variables.

13. How to execute a PHP script from the command line?

Here, we mentioned the following PHP command line to run the PHP program:

• Open terminal or command line window.
• Go to the specified folder or directory where PHP files are present.
• Then, we can run PHP code using the command php file_name.php
• Start the server for testing the php code using the command php -S localhost:port -t your_folder/

14. What is the most used method for hashing passwords in PHP?

The crypt() function in PHP is another option for hashing passwords, offering a wide variety of hashing algorithms like SHA-1, SHA-256, and MD5. While these algorithms are fast and efficient, they are no longer considered secure for hashing passwords due to their vulnerability to brute-force and rainbow table attacks.

15. Does JavaScript interact with PHP?

Yes, JavaScript can interact with PHP, typically through AJAX (Asynchronous JavaScript and XML). JavaScript sends requests to PHP on the server, and PHP processes these requests and returns data (often in JSON or HTML format) to JavaScript for further manipulation on the client side without reloading the page.

Common use cases include

• Submitting forms without refreshing the page.
• Fetch data from a server dynamically.
• Updating content on a page based on user actions.

16. Explain the main types of errors.

The three main types of errors in PHP are:

• Notices: Notices are non-critical errors that can occur during the execution of the script. These are not visible to users. Example: Accessing an undefined variable.
• Warnings: These are more critical than notices. Warnings don’t interrupt the script execution. By default, these are visible to the user. Example: include() a file that doesn’t exist.
• Fatal: This is the most critical error type, which, when occurs, immediately terminates the execution of the script. Example: Accessing a property of a non-existent object or require() a non-existent file.

17. How do you define a constant in PHP?

The define() function is a fundamental feature in PHP for PHP Defining Constants.

• It serves to create and retrieve the value of a constant, which is an identifier whose value remains fixed throughout the execution of a script.
• Unlike variables, constants are defined without the dollar sign ($) and cannot be altered or undefined once set.
• Constants are commonly used to store unchanging values such as the domain name of a website (e.g., www.geeksforgeeks.org).

18. What are the popular frameworks in PHP?

Some of the most popular PHP frameworks are:

• Laravel
• CodeIgniter
• Symfony
• CakePHP
• Yii
• Zend Framework
• Phalcon
• FuelPHP
• PHPixie
• Slim

19. What are the popular Content Management Systems (CMS) in PHP?

Some popular Content Management Systems (CMS) written in PHP include:

• WordPress: WordPress is a free and open-source Content Management System(CMS) framework. It is the most widely used CMS framework of recent times.
• Joomla: Joomla is a free and open-source content management system (CMS) for distributing web content. It follows the model-view-controller web application framework that can be used independently.
• Magento: It is an open-source and e-commerce platform to develop online business.
• Drupal: It is a content management system (CMS) platform developed in PHP and distributed under the GNU (General Public License).

20. What is the purpose of the break and continue statement?

The break and continue statements are used in loops and switch statements to control the flow of execution.

• break: The break statement immediately terminates the whole iteration of a loop, and the program control resumes at the next statement following the loop.
• continue: The continue statement skips the current iteration and brings the next iteration early. The continue 2 acts as a terminator for case and skips the current iteration of the loop.

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

The PHP count() function counts the number of elements present in the array. The function might return 0 for the variable that has been set to an empty array. Also, for the variable which is not set, the function returns 0.

22. What are the different types of loops in PHP?

PHP supports four different types of loop which are listed below:

• for loop
• while loop
• do-while loop
• foreach loop

PHP Interview Questions for Intermediate

23. What is the main difference between PHP 4 and PHP 5?

The main differences between PHP 4 and PHP 5 are:

Object-Oriented Programming (OOP) Support:

• PHP 4 had limited object-oriented support. It used the concept of “objects” but lacked many OOP features like access modifiers (private, protected), constructors/destructors, and inheritance.
• PHP 5 introduced full-fledged object-oriented programming with improved support for classes, interfaces, abstract classes, constructors, destructors, and access modifiers.

Performance and Features:

• PHP 4 was based on a simpler Zend engine, which lacked several optimizations present in newer versions.
• PHP 5 introduced the Zend Engine II, providing better performance, more efficient memory handling, and additional features like exception handling, reflection, and PDO (PHP Data Objects) for database abstraction.

XML Support:

• PHP 4 had limited XML support.
• PHP 5 included more robust XML support, with built-in extensions like DOM and SimpleXML for easier XML parsing and manipulation.

Error Handling:

• PHP 4 used traditional error handling via the $php_errormsg global variable.
• PHP 5 introduced exception handling using try, catch, and throw keywords for better control and readability.

Support for New Extensions:

• PHP 5 introduced many new extensions, including PDO for database interaction and SOAP for web services, which were not available in PHP 4.

24. Explain the importance of Parser in PHP.for each

A PHP parser is a tool that converts PHP source code into a format that the computer can interpret and execute. It translates the PHP instructions into machine-readable code, allowing the server to process and run the script. You can parse PHP code using the token_get_all() function, which breaks down the PHP code into an array of tokens that represent different parts of the code (like variables, keywords, operators, etc.).

25. What is the difference between for and foreach loop in PHP?

26. How can PHP and HTML interact?

PHP scripts can generate HTML content and pass information from HTML to PHP. While PHP is a server-side language, HTML operates on the client side. PHP processes data on the server and returns results as strings, objects, or arrays, which can then be displayed within HTML. This interaction allows both languages to complement each other effectively.

27. What are the main error types, and how do they differ?

There are various types of errors in PHP, but it contains ,four main types of errors.

• Parse error or Syntax Error: This is the type of error made by the programmer in the source code of the program. Parse errors can be caused dues to non-closed quotes, missing or extra parentheses, non-closed braces, missing semicolon, etc.
• Fatal Error: It is the type of error where PHP compiler understands the PHP code but it recognizes an undeclared function. It means that function is called without the definition of the function.
• Warning Errors: The main reason for warning errors are including a missing file. This means that the PHP function call the missing file.
• Notice Error: It is similar to warning error. It means that the program contains something wrong but it allows the execution of script.

28. What is inheritance in PHP ?

Inheritance in PHP is an object-oriented programming (OOP) concept where a class (called the child or subclass) can inherit properties and methods from another class (called the parent or superclass). This allows the child class to reuse code from the parent class and extend or modify its functionality.

29. Is PHP supports multiple inheritance ?

No, PHP does not support multiple inheritance directly, meaning a class cannot inherit from more than one class. A class can only inherit from one parent class, which is a limitation of PHP’s inheritance model. However, PHP allows for multiple inheritance through interfaces. A class can implement multiple interfaces, enabling it to inherit behavior from more than one source.

30. What are Traits in PHP ?

Traits in PHP are a mechanism for code reuse in single inheritance languages like PHP. They allow you to include methods in a class without using inheritance, providing a way to share functionality across multiple classes.

• Code Reuse: Traits allow you to reuse methods across different classes without duplicating code.
• Conflict Resolution: If multiple traits define a method with the same name, PHP requires you to resolve the conflict by explicitly defining which method to use.
• No Instantiation: Traits cannot be instantiated on their own, they must be included in a class.

31. What is difference between GET and POST?

GET: It requests data from a specified resource. In this method, the data is sent as URL parameters that are usually strings of name and value pairs separated by ampersands (&).

<?php
    $_GET['variable_name'];
?>

POST: In this method the data is sent to the server as a package in a separate communication with the processing script. Data sent through POST method will not be visible in the URL.

<?php
    $_POST['variable_name'];
?>

32. What is the difference between the unset() and unlink() functions ?

Unlink() function: The unlink() function is an inbuilt function in PHP which is used to delete a file.

• The filename of the file which has to be deleted is sent as a parameter and the function returns True on success and False on failure.
• The unlink() function in PHP accepts two-parameters filename and context.

Unset() function: The Unset() function is an inbuilt function in PHP which is used to remove the content from the file by emptying it.

• It means that the function clears the content of a file rather than deleting it.
• The unset() function not only clears the file content but also used to unset a variable, thereby making it empty accepts a single parameter variable.

33. If x = 10 and y = “10” then what does the condition x === y returns ?

The condition x === y checks for both value and type equality in PHP.

• x = 10 is an integer.
• y = “10” is a string.

Since the values are the same (10), but their types are different (integer vs string), the condition x === y will return false.

In PHP:

• === checks both the value and type.
• == only checks the value, allowing type conversion.

<?php

​

    $x = 10;  

    $y = "10";

​

    var_dump($x === $y); 

?>

bool(false)

34. What is Nullable types in PHP ?

This feature is new to PHP, Nullable adds a leading question mark indicate that a type can also be null.

function geeks(): ?int  {
        return null;
    }
    

35. What is the maximum size of a file that can be uploaded using PHP ?

By default maximum upload file size for PHP scripts is set to 128 megabytes. But you can change it. The maximum size of any file that can be uploaded on a website written in PHP is determined by the values of max_size that can be posted or uploaded, mentioned in the php.ini file of the server.

36. What are PHP streams?

Streams are a way of abstracting input/output (I/O) operations, allowing you to work with various data sources (like files, network connections, or even in-memory data) in a consistent manner. Streams represent a generalization of I/O operations, enabling data to be read from or written to a resource.

37. What is autoloading in PHP?

Autoloading in PHP is a mechanism that automatically loads classes, interfaces, and traits when they are needed, without explicitly requiring you to include or require the file where they are defined. This improves code organization, reduces the need for multiple include or require statements, and helps manage dependencies efficiently.

How Autoloading Works

• When a class is referenced (for example, when you instantiate a class or call a method), PHP automatically looks for the corresponding file containing the class definition.
• If the file is not already included in the script, PHP uses an autoloader function to locate and load the class file.

38. How can you prevent Cross-Site Scripting (XSS) in PHP?

Cross-Site Scripting (XSS) is a vulnerability where an attacker injects malicious scripts into web pages viewed by other users. To prevent XSS attacks in PHP use-

Escape Output (HTML Encoding): Encode user-generated content to prevent it from being treated as executable code.

echo htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');

Validate Input: Sanitize and validate user input to ensure it follows the expected format.

$email = filter_var($_POST['email'], FILTER_SANITIZE_EMAIL);

Use Content Security Policy (CSP): Restrict which content can be loaded to reduce XSS risks.

header("Content-Security-Policy: default-src 'self'; script-src 'self';");

39. What is the difference between crypt() and password_hash()?

40. How do you create and use an interface in PHP?

An interface in PHP defines a contract for classes that implement it. It specifies methods that the implementing classes must define, but it does not provide the method implementation itself.

• Define an Interface: Use the interface keyword to define an interface. The methods declared inside the interface must be public.

interface Animal {
    public function speak();
}

• Implement the Interface: A class can implement an interface using the implements keyword. The class must define all the methods declared in the interface.

class Dog implements Animal {
    public function speak() {
        echo "Woof!";
    }
}

• Using the Interface: Create an object of the class that implements the interface and call the method.

$dog = new Dog();
$dog->speak();

41. How to send an email using PHP?

In PHP, we can send an email using the built-in mail() function. Here’s a simple way to send an email:

Synatx

mail($to, $subject, $message, $headers);

• to: The recipient’s email address.
• $subject: The subject of the email.
• $message: The body content of the email.
• $headers: Additional headers, like “From”, “Reply-To”, etc. (optional).

PHP Interview Questions for Advanced

42. What is dependency injection in PHP?

Dependency Injection (DI) is a design pattern used to implement Inversion of Control (IoC), where an object’s dependencies (other objects it depends on) are provided to it rather than the object creating them itself.

43. Explain the SOLID principles in PHP.

The SOLID principles are a set of five design principles that help developers write better, more maintainable, and scalable object-oriented code. They are widely used in PHP development to improve code readability, flexibility, and reusability.

• Single Responsibility Principle (SRP) : A class should have only one reason to change, meaning it should only have one job or responsibility.
• Open/Closed Principle (OCP) : A class should be open for extension but closed for modification.
• Liskov Substitution Principle (LSP) : Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.
• Interface Segregation Principle (ISP) : A client should not be forced to depend on interfaces it does not use.
• Dependency Inversion Principle (DIP) : High-level modules should not depend on low-level modules. Both should depend on abstractions.

44. How do you optimize PHP applications for performance?

To optimize PHP applications for better performance, you can implement several techniques to minimize resource usage and enhance execution speed.

• Use Opcode Caching (e.g., OPcache): Caching the compiled PHP code in memory reduces the need for PHP to parse and compile scripts on every request.
• Optimize Database Queries: Inefficient database queries can slow down the application.
• Use Content Delivery Networks (CDNs): Offloading static content to CDNs reduces server load and speeds up content delivery by caching resources closer to users.
• Enable Compression (e.g., GZIP): Compressing the output reduces the size of HTML, CSS, and JavaScript files, which speeds up page loading.
• Cache Dynamic Content: Caching avoids repeated computations for dynamic content, improving response time.
• Use Asynchronous Operations: Offload non-critical tasks to avoid blocking the main thread and improve application responsiveness.
• Profile and Benchmark Code: Identifying slow parts of the application helps optimize performance.

45. What are middleware in PHP frameworks?

Middleware in PHP frameworks are components that sit between the request and response cycle. They allow you to filter, modify, or handle requests before they reach the application’s core logic or after the response is generated but before it is sent to the client.

• Purpose: Middleware handles tasks like authentication, logging, request validation, and modifying HTTP responses.
• Usage: They are executed in a specific order, with each middleware passing control to the next until the final response is returned.
• Example: In frameworks like Laravel, middleware can handle tasks like ensuring the user is authenticated before accessing certain routes.

46. What are the steps to create a new database using MySQL and PHP?

The four main steps used to create a new MySQL database in PHP are given below:

• A connection establishment is done to the MySQL server using the PHP script.
• The connection is validated. If the connection is successful, then you can write a sample query to verify.
• Queries that create the database are input and later stored into a string variable.
• Then, the created queries will be executed one after the other

47. Write a function to reverse a string without using strrev().

<?php

function reverse($str) {

    $reversed = "";

    for ($i = strlen($str) - 1; $i >= 0; $i--) {

        $reversed .= $str[$i];

    }

    return $reversed;

}

​

echo reverse("GeeksforGeeks"); 

?>

skeeGrofskeeG

• Initialize an empty string $reversed.
• Loop through the input string from last character to first.
• Append each character to $reversed.
• Return the reversed string.

48. How would you remove duplicate values from an array in PHP?

<?php

function remove($arr) {

    return array_values(array_unique($arr));

}

​

$numbers = [1, 2, 2, 3, 4, 4, 5];

print_r(remove($numbers));

?>

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

• array_unique($arr): Removes duplicate values from the array $arr.
• array_values(): Re-indexes the array to ensure the keys are in numerical order starting from 0.

49. Implement a function to check if a string is a palindrome

<?php

function isPalindrome($str) {

    return strtolower($str) === strtolower(strrev($str));

}

​

echo isPalindrome("madam") ? "Palindrome" : "Not a Palindrome";

?>

Palindrome

• Remove non-alphanumeric characters and convert to lowercase.
• Reverse the string and compare with the original.
• Returns True if the string is a palindrome, otherwise False.

50. Write a PHP function to find the second largest number in an array.

<?php

function secondLargest($arr) {

    $arr = array_unique($arr);

    rsort($arr);

    return $arr[1] ?? null;

}

​

$nums = [10, 20, 4, 45, 99, 99];

echo secondLargest($nums); 

?>

45

• array_unique($arr): Removes duplicate values from the array.
• rsort($arr): Sorts the array in descending order.
• $arr[1] ?? null: Returns the second element (second largest number). If the array has less than two unique elements, it returns null.