Top 50+ PHP Interview Questions and Answers [2025]

PHP Interview Questions for Freshers

For those new to PHP, interviews typically begin with straightforward PHP questions that assess your understanding of core concepts. From variables and arrays to control structures and basic syntax, these questions evaluate your comfort level with writing and interpreting PHP scripts.

1. What Is PHP?

PHP (Hypertext Preprocessor) is a widely used, open-source, server-side scripting language designed specifically for web development. It is embedded within HTML and is especially suited for creating dynamic and interactive web pages. PHP allows developers to manage databases, handle forms, perform server-side scripting, and build entire web applications. It is platform-independent, supports a wide range of databases, and is known for its simplicity, flexibility, and speed in web-based development.

2. What PHP Used to Be Called?

This is one of the commonly asked PHP interview questions. PHP was originally called Personal Home Page Tools when it was created by Rasmus Lerdorf in 1994. It started as a set of Common Gateway Interface (CGI) scripts to track visits to his online resume.

As its functionality expanded, it was renamed PHP: Hypertext Preprocessor, a recursive acronym, reflecting its evolution into a full server-side scripting language for web development.

3. What Are Some of the Common Applications of PHP?

PHP is commonly used to perform the following tasks:

• Working with files: It is possible to create, read, write, delete, or close files using PHP.
• Handling forms: From collecting user input to storing or emailing it, PHP facilitates form submissions.
• Interacting with databases: You can insert or update records in a database through PHP scripts.
• Managing cookies: PHP allows setting and retrieving cookie values, useful for remembering user preferences.
• Restricting access to pages: PHP can limit access to pages for logged-in users only.
• Encrypting data: PHP can encrypt data to keep sensitive information secure.

4. What Are the Popular Frameworks in PHP?

This is one of the frequently asked PHP interview questions. Some of the most popular PHP frameworks are:

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

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5. Name the Popular Content Management Systems (CMS) in PHP

Here are some of the popular Content Management Systems:

• WordPress
• Joomla
• Magento
• Drupal

6.What Does PEAR Stand for?

PEAR stands for PHP Extension and Application Repository. It is a framework and distribution system for reusable PHP components, providing a structured library of code for common tasks like authentication, caching, and database access. PEAR helps developers avoid reinventing the wheel by offering standardized packages that can be easily installed and integrated into PHP projects.

7. Is PHP a Case-Sensitive Language?

PHP is partially case-sensitive. Variables are case-sensitive in PHP, so $name, $Name, and $NAME are treated as three distinct variables. Function names are case-insensitive; they can be defined in lowercase and invoked in uppercase, and PHP will recognize them. This applies to any user-defined function. So while PHP is partially case-sensitive, it offers some flexibility depending on what is being referenced.

8. What Are the Different Types of Loops in PHP?

This is one of the popular PHP interview questions. PHP comprises four main types of looping structures, each used for repeating blocks of code depending on some condition:

• for loop: Used when the number of iterations is known before the loop starts.
• while loop: Executes as long as the condition is true; the condition is checked before each iteration.
• do-while loop: Similar to while, but guarantees at least one execution as the condition is checked after the code runs.
• foreach loop: Specifically for iterating through arrays, simplifying access to each element without a counter.

9. How Do You Declare a Variable in PHP?

Declaring a variable in PHP uses a dollar sign followed by the variable name. For example: $age = 30; and $name = "Alex";. PHP assigns the type based on the assigned value. Variable names are case-sensitive, so $Name and $name are treated differently.

10. What Are the Different Types of PHP Variables?

This is one of the frequently posed PHP interview questions. There are 8 data types in PHP that are used to construct the variables:

• Integer: Whole numbers without a decimal point, e.g., 4195.
• Double: Floating-point numbers, e.g., 3.14159 or 49.1.
• Boolean: Values can be either true or false.
• NULL: A special type with only one value: NULL.
• String: Sequences of characters, e.g., ‘PHP supports string operations.’
• Array: Named and indexed collections of values.
• Object: Instances of programmer-defined classes containing values and functions.
• Resource: Special variables holding references to external resources.

11. What Is the Default File Extension of PHP Files?

The default file extension for PHP files is .php. This tells the web server to process the file using the PHP interpreter before sending the output to the browser. Older or alternate extensions like .php3, .php4, or .phtml were used historically, but .php is now standard and widely recognized for server-side scripting.

12. What Are the Rules for Naming a PHP Variable?

PHP variable naming basics:

• Must begin with a dollar sign ($) followed by a letter or underscore; numbers cannot come first.
• After the initial character, only letters, numbers, and underscores are allowed.
• Variable names are case-sensitive; for example, $dataSet and $DataSet are different.
• Avoid using PHP reserved keywords like if, foreach, class, etc.
• Variable names should be descriptive and meaningful for readability and maintainability.

13. Explain the Purpose of $_GET and $_POST

$_GET and $_POST are built-in PHP arrays that collect form data. $_GET gathers values from the URL (e.g., page.php?user=Tom), useful for search filters or bookmarking. $_POST collects values hidden from the URL, like passwords or uploaded files. These arrays let you access submitted form data and decide how to handle it.

14. What Is the Difference Between include() and require()?

Both include() and require() import code from another file. The key difference is how missing files are handled: include() throws a warning and continues execution, while require() triggers a fatal error and stops further execution. Use require() for essential files like configurations or database connections; otherwise, include() is sufficient.

15. What Are PHP Sessions?

A session in PHP stores user information across multiple pages. For example, when someone logs in, a session tracks their login details until logout or browser closure. PHP uses a unique session ID stored in a cookie to manage this. Sessions are more secure than query strings because data isn’t passed in the URL.

16. How Do You Start a Session in PHP?

Starting a session uses the session_start() function, which must be called before any output is sent to the browser. It either initiates a new session or reactivates an existing one, allowing storage of user data through $_SESSION. For example, $_SESSION['user_id'] can track a logged-in user. End the session with session_destroy() during logout to clear stored data.

17. What Is a Cookie in PHP?

In PHP, a cookie is a small piece of data stored on the user's browser by a web server. It can hold information like user preferences, login details, or session identifiers. PHP uses the setcookie() function to create cookies, which are sent with HTTP headers and can be accessed on subsequent requests to maintain state across pages.

18. What Is the Difference Between == and === in PHP?

The operator == checks equality of values after type conversion, while === checks both value and data type. For example:

5 == "5";   // true — values match after coercion
5 === "5";  // false — types differ (integer vs string)

Using === is best practice when strict comparison is needed to avoid unexpected behavior.

19. How Do You Connect to a MySQL Database Using PHP?

This is listed among the top PHP interview questions. You can use either the MySQLi extension or PHP Data Objects (PDO). Both support secure, object-oriented connections and error handling.

MySQLi (Object-Oriented):

$host     = 'localhost';
$user     = 'root';
$pass     = '';
$dbname   = 'my_database';

$conn = new mysqli($host, $user, $pass, $dbname);
if ($conn->connect_error) {
    die('Connection failed: ' . $conn->connect_error);
}
// use $conn for queries...

PHP Data Objects:

try {
    $dsn  = 'mysql:host=localhost;dbname=my_database;charset=utf8';
    $pdo  = new PDO($dsn, 'root', '', [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    ]);
    // use $pdo for prepared statements...
} catch (PDOException $e) {
    die('Connection failed: ' . $e->getMessage());
}

MySQLi is simpler for MySQL-only projects, while PDO offers database-agnostic flexibility, built-in prepared statements, and more robust error handling.

20. What Is the Purpose of die() in PHP?

This is one of the commonly asked PHP interview questions. The die() function outputs an optional message and immediately terminates the script. It is an alias of exit().

Example:

$file = fopen('config.ini', 'r') or die('Unable to open config file');

It accepts an optional parameter (string or integer) and is commonly used for simple error handling to halt execution when a critical condition isn’t met.

PHP Interview Questions for Intermediate

Once you've mastered the basics, interviewers will expect a deeper understanding of PHP concepts and how they’re applied in real-world scenarios. PHP interview questions at the intermediate level typically focus on working with forms, sessions, file handling, error management, object-oriented programming, and integrating PHP with other technologies.

21. What Are the Different Types of Arrays in PHP?

This is one of the go-to PHP interview questions. PHP arrays come in different types, each suited for specific use cases. The main types are:

• Indexed arrays: Numeric arrays with sequential indices starting from 0. Example: $fruits = array("Apple", "Banana", "Orange");
• Associative arrays: Key-value pairs allowing string or integer keys. Example: $student = array("name" => "John Smith", "age" => 20, "university" => "ABC University");
• Multidimensional arrays: Arrays within arrays, useful for nested data structures. Example: $matrix = array(array(1,2,3), array(4,5,6), array(7,8,9));

22. What Is the Difference Between an Array and a List in PHP?

An array can hold multiple values under one variable and may be indexed or associative. A list typically refers to a flat, numerically indexed array or the use of the list() function to extract values from an array. They are related but differ in how they are handled or interpreted.

23. Explain the Importance of the Parser in PHP

A parser translates PHP code into a format the interpreter can execute. It performs:

• Syntax checking: Ensures code follows PHP grammar and structure, catching errors early.
• Code translation: Converts human-readable PHP into opcode that the Zend Engine can execute.
• Security and optimization: Helps optimize performance and guards against injection flaws or misuse.

24. How Can PHP Interact with HTML?

PHP interacts with HTML by embedding PHP code directly within HTML files using <?php ... ?> tags. The PHP code runs on the server, generating dynamic content such as text, forms, or database results, which is then sent as plain HTML to the browser. This allows web pages to display changing content based on user input, sessions, or backend data.

25. How Do You Redirect a Page in PHP?

Use the header() function with a Location URL and then stop execution with exit(). This must be done before any HTML output.

<?php
header("Location: newpage.php");
exit();
?>

26. What Is the Difference Between session_unset() and session_destroy()?

In PHP, session_unset() removes all session variables but keeps the session active, allowing new variables to be set. session_destroy() completely ends the session, deleting the session data on the server, but it doesn’t automatically remove session variables from the current script. Usually, session_unset() is used for clearing data, while session_destroy() is for terminating the session.

27. How Can Error Reporting Be Enabled in PHP?

This is one of the commonly asked PHP interview questions. Activate error reporting at the start of the script:

error_reporting(E_ALL);
ini_set('display_errors', 1);

Use error_reporting(E_ALL) to report all errors and ini_set('display_errors', 1) to display them. Disable display in production for security.

28. What Are the Different Types of Errors in PHP?

Main error types:

• Parse errors: Code violates syntax rules, preventing execution.
• Fatal errors: Critical runtime errors that stop script execution.
• Warning errors: Non-fatal issues that allow script execution to continue.
• Notice errors: Informational messages about minor code issues.
• Deprecated errors: Indicate outdated features that should be avoided.

29. What Is the Use of the break Statement in PHP?

In PHP, the break statement is used to exit loops or switch statements prematurely. When executed, it immediately stops the current loop iteration or ends a switch case, transferring control to the code following the loop or switch. It helps prevent unnecessary iterations and allows conditional termination of repetitive or branching structures in scripts.

30. What Is the Use of the continue Statement in PHP?

In PHP, the continue statement skips the rest of the current loop iteration and moves to the next one. It’s used inside for, while, do-while, or foreach loops to bypass certain code when a condition is met, without exiting the loop entirely. This helps control loop flow while avoiding unnecessary processing in specific cases.

31. What Is the Difference Between the GET and POST Methods?

GET appends data to the URL and is visible in the browser. It is suitable for retrieving information without changing server state and can be bookmarked or shared. POST sends data in the request body, keeping it hidden from the URL. It is better for sensitive data, file uploads, or submitting forms with large datasets.

32. What Is the Difference Between unset() and unlink()?

This is one of the frequently asked PHP interview questions. In PHP, unset() deletes a variable from memory, making it undefined in the current script. It affects only variables, arrays, or object references. unlink(), on the other hand, deletes a file from the server’s filesystem. So, unset() manages data in code, while unlink() manages files stored on disk. They operate in completely different contexts.

33. What Are Traits in PHP?

In PHP, traits are a mechanism for code reuse in single inheritance. They allow developers to include methods and properties in multiple classes without using inheritance. Traits help avoid duplication when multiple classes share similar functionality. You define a trait with the trait keyword and include it in a class using use, giving flexibility in organizing reusable code.

34. What Is Inheritance in PHP?

In PHP, inheritance allows a class (child) to acquire properties and methods from another class (parent). This enables code reuse and hierarchical relationships between classes. The child class can use, override, or extend the parent’s functionality. PHP uses the extends keyword to implement inheritance, supporting single inheritance, where a class can inherit from only one parent class.

35. Does PHP Support Multiple Inheritance?

No, PHP does not support multiple inheritance directly, meaning a class cannot extend more than one parent class. To achieve similar functionality, PHP uses traits, which allow a class to include methods and properties from multiple sources. This provides code reuse across classes without the complexity and conflicts of traditional multiple inheritance.

36. What Are Associative Arrays in PHP?

In PHP, associative arrays are arrays where keys are strings instead of numbers. Each key maps to a specific value, allowing easy access by meaningful names rather than numeric indexes. They are useful for storing data like user information or configurations. You create them using the syntax $array['key'] = 'value'; and access values via their corresponding keys.

37. What Is the Difference Between explode() and implode() in PHP?

explode() splits a string into an array using a delimiter, while implode() joins array elements into a string using a glue.

• explode(): Converts a string into an array. Syntax: explode(delimiter, string)
• implode(): Converts an array into a string. Syntax: implode(glue, array)

38. How to Execute a PHP Code from the Command Line?

This is one of the frequently asked PHP interview questions. PHP can be run from the command line using the PHP CLI. Methods include:

• Run a PHP file: php script.php
• Run inline code: php -r 'echo "Hello!";'
• Pass arguments: php args.php val1 val2, accessed via $argv
• Interactive mode: php -a
• Background execution: php script.php &
• Built-in server: php -S localhost:8000

39. Name Some of the Functions in PHP

PHP provides a variety of built-in functions that help developers work with strings, arrays, files, and more. Some commonly used functions include:

• preg_match(): A function used to match regular expressions in a string.
• explode(): Splits a string into an array based on a delimiter.
• preg_match(): Performs a regular expression match. Returns whether a match is found or not.
• preg_split(): Splits a string into an array using a regular expression as a delimiter.
• strlen(): Returns the length of a string. Useful for string manipulation.
• array_merge(): Merges two or more arrays into one.
• file_get_contents(): Reads the contents of a file into a string. Convenient for reading file data.
• json_encode(): Encodes a PHP variable into a JSON format string, often used for sending data to APIs or front-end applications.
• header(): Sends raw HTTP headers to the browser. Often used for redirects or setting content types.

40. What Is Escaping, and Its Types?

Escaping adds special characters to ensure data is interpreted safely. Types include:

• HTML escaping: Use htmlspecialchars() or htmlentities() to prevent XSS.
• URL escaping: Use urlencode() or rawurlencode() for safe URL transmission.
• JavaScript escaping: Encode PHP data for safe JS insertion, often with json_encode().
• SQL escaping: Prevent SQL injection via mysqli_real_escape_string() or prepared statements.
• Shell argument escaping: Use escapeshellarg() or escapeshellcmd() for secure command-line arguments.

PHP Interview Questions for Advanced

At the advanced stage, PHP interview questions are designed to assess your expertise in PHP architecture, design patterns, performance optimization, and a deep understanding of the language’s core functionalities. This includes topics like namespaces, traits, late static binding, multithreading alternatives, memory management, and integration with tools and frameworks.

41. How Would You Remove Duplicate Values from an Array in PHP?

Use the array_unique() function to remove duplicate values from an array. Example:

<?php
function remove($arr) {
    return array_values(array_unique($arr));
}

$numbers = [1, 2, 2, 3, 4, 4, 5];
print_r(remove($numbers));
?>

42. What Is Late Static Binding in PHP?

This is one of the go-to PHP interview questions. Late Static Binding (LSB) determines the class context of static calls at runtime rather than at compile-time. Using static:: instead of self:: allows child classes to override static methods or properties correctly. Example:

class A {
  public static function who() { echo __CLASS__; }
  public static function test() { static::who(); }
}

class B extends A {
  public static function who() { echo __CLASS__; }
}

B::test(); // Outputs "B"

43. How Does PHP Handle Multibyte Characters?

PHP handles multibyte characters using the Multibyte String (mbstring) extension, which allows proper processing of UTF-8 and other multibyte encodings. Functions like mb_strlen(), mb_substr(), and mb_strpos() correctly count, extract, and search characters without breaking them. Regular string functions may fail with multibyte data.

Example:

$text = "こんにちは";
echo mb_strlen($text, "UTF-8"); // Outputs 5

Here, mb_strlen() counts characters, not bytes, ensuring accurate handling of multibyte text.

44. How to Terminate the Execution of a Script in PHP?

In PHP, you can terminate script execution using the exit() or die() functions. Both stop the script immediately and optionally display a message or return a status code. They are often used for error handling, stopping execution if conditions aren’t met, or after sending output to the browser.

Example:

if(!$userLoggedIn) {
    die("Access denied.");
}

45. How Can Cross-Browser PHP Automation Testing Be Scaled Efficiently?

The automation testing of a PHP application is best done across several browsers and operating systems using a cloud-based platform, eliminating the need for local setup. Cloud testing platforms like LambdaTest allow:

• Selection of browsers and operating systems in multiple versions.
• CI/CD integration for automated testing pipelines.
• Access to test execution logs, screenshots, and video recordings for debugging.

46. What Is OPcache in PHP?

OPcache is a PHP extension focused on improving the performance of PHP applications. Normally, PHP scripts are parsed and compiled into bytecode every time a request is made, which can be time-consuming for large applications. OPcache solves this by storing precompiled script bytecode in shared memory, so PHP does not need to repeatedly load and parse scripts on each request.

Key Benefits:

• Faster execution: Since scripts are precompiled, PHP can execute code without parsing and compiling, reducing response times.
• Reduced CPU load: Less parsing and compiling means lower CPU usage on the server, especially under heavy traffic.
• Improved scalability: Applications can handle more requests simultaneously, benefiting high-traffic websites.
• Memory efficiency: Bytecode is stored in shared memory, avoiding repeated memory allocations for the same script across requests.

OPcache is easy to enable in PHP by configuring the php.ini file. Typical settings include opcache.enable=1 to turn it on, and opcache.memory_consumption to allocate memory for storing precompiled scripts.

47. What Is Composer?

Composer is a dependency manager for PHP. It automates installation and updates of libraries defined in composer.json, maintains consistent versions across environments, and supports autoloading for classes.

Key Features:

• Dependency management: Automatically installs and updates all project libraries based on the specifications in the composer.json file.
• Version control: Ensures consistent versions across different environments (development, staging, production).
• Autoloading: Provides automatic loading of PHP classes without needing manual include or require statements, making code cleaner and more maintainable.
• Ease of use: Simple commands like composer install or composer update handle all dependency management tasks efficiently.

To get started, developers create a composer.json file listing the required packages. Then, running composer install fetches and installs all dependencies into the vendor directory, with autoloading ready for immediate use.

48. How to Connect to a URL in PHP?

PHP can connect to URLs using the cURL library, which is included by default in PHP. cURL (Client URL) allows you to send HTTP requests, receive responses, and interact with remote servers or APIs efficiently.

Steps to connect using cURL:

• Initialize cURL: Start a new session with curl_init().
• Set URL and Options: Use curl_setopt() to define the URL and options, such as POST/GET requests and data fields.
• Execute Request: Run the request with curl_exec() to fetch the response.
• Close Session: End the cURL session using curl_close() to free up resources.

Example:

?php
// Step 1: Initialize cURL
$ch = curl_init();

// Step 2: Set URL and options
$url = 'http://www.example.com';
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, 'param1=value1&param2=value2');

// Step 3: Execute cURL
$response = curl_exec($ch);

// Step 4: Close cURL
curl_close($ch);

// Display the response
echo $response;
?

With cURL, you can also handle headers, cookies, timeouts, SSL verification, and authentication, making it versatile for web scraping, API calls, and automated requests.

49. What Are Superglobals in PHP?

Superglobals in PHP are built-in variables that are always accessible in all scopes throughout a script. You do not need to use global to access them inside functions or classes. These variables provide quick access to information about requests, sessions, server details, environment, and more.

Key Superglobals include:

• $_GET: Contains data sent via URL parameters. Useful for retrieving query string values.
• $_POST: Holds data submitted via HTML forms using the POST method. Suitable for sensitive data like passwords.
• $_REQUEST: Collects data from $_GET, $_POST, and $_COOKIE.
• $_SERVER: Provides information about headers, paths, and script locations.
• $_SESSION: Stores session data across multiple pages for logged-in users.
• $_COOKIE: Retrieves values stored in cookies.
• $_FILES: Handles file uploads via HTTP POST.
• $_ENV: Contains environment variables from the server.
• $GLOBALS: Stores all global variables in the script, accessible anywhere.

These superglobals are pre-defined by PHP and provide an efficient way to access critical information without needing to declare them globally.

50. How Do You Pass Data from One PHP Page to Another?

Data can be passed from one PHP page to another using methods such as URL parameters, form submission, sessions, cookies, or by storing data in a database and retrieving it on the subsequent page.

• URL parameters: Data can be appended to the URL using query strings. Example: page.php?user=Tom&age=25. Accessible via $_GET.
• Form submission: Use HTML forms with method="POST" or method="GET". POST hides data in the request body, while GET appends it to the URL. Accessed via $_POST or $_GET.
• Sessions: Store data on the server using $_SESSION. Start with session_start() on every page that uses session data. Useful for persisting login info or preferences.
• Cookies: Small pieces of data stored on the user’s browser via setcookie(). Accessed using $_COOKIE. Good for remembering preferences or lightweight data.
• Database storage: Save data in a database on one page and retrieve it on another. Ideal for large or persistent datasets shared across users.

51. How Can You Compare Objects in PHP?

Comparing objects in PHP is a valuable way to determine if two objects are equal. The comparison is based on the properties of the object and their values. PHP offers a built-in function var_dump() to inspect objects and compare them effectively.

Comparing objects in PHP involves checking whether two objects are considered equal or identical. PHP provides multiple ways to compare objects depending on the level of comparison required:

Features:

• Equality (==): Checks if two objects have the same properties and values, regardless of whether they are instances of the same class. Example: $obj1 == $obj2.
• Identity (===): Checks if two objects reference the exact same instance. For example, $obj1 === $obj2 returns true only if both variables point to the same object in memory.
• var_dump(): Can be used to inspect and compare object properties manually for debugging purposes.
• Custom comparison: For more complex scenarios, you can define a method inside the class, like isEqual($otherObject), to compare selected properties according to business logic.

52. What Design Patterns Have You Used in Your PHP Projects?

Common design patterns include:

• Singleton pattern: For shared instances across the application.
• Factory pattern: For object creation without specifying the exact class.
• Model-View-Controller (MVC): For structuring applications efficiently.
• Dependency injection: For managing class dependencies and improving testability.