Top Interview Questions for PHP Developers in 2025

1. What Is PHP and How Does It Work?

The most basic question you’ll likely face in any PHP interview is about the language itself. Interviewers want to assess your understanding of PHP and its role in web development.

PHP (Hypertext Preprocessor) is a server-side scripting language used to develop dynamic and interactive websites. It is embedded in HTML and can interact with databases, handle form data, and generate dynamic content. PHP code is executed on the server, and the result is sent to the client's browser.

2. What Are the Key Features of PHP?

When asked about the key features of PHP, highlight its capabilities and advantages. Some important features include:

• Server-Side Execution: PHP runs on the server and generates dynamic content.

• Database Integration: PHP easily integrates with databases like MySQL, PostgreSQL, and SQLite.

• Cross-Platform Compatibility: PHP runs on various operating systems like Windows, Linux, and macOS.

• Built-in Libraries: PHP provides a rich set of libraries for tasks like image manipulation, PDF generation, and more.

• Support for OOP: PHP supports Object-Oriented Programming (OOP), enabling modular, maintainable, and reusable code.

3. What Are the Differences Between include and require in PHP?

This is a common PHP question that checks your understanding of PHP file inclusion functions.

• include: Includes a specified file during the execution of the script. If the file is not found, it generates a warning, but the script continues execution.

• require: Similar to include, but if the file is not found, it generates a fatal error and stops the script execution.

While both are used to include external files, the key difference is how errors are handled.

4. What Are Sessions and Cookies in PHP?

Sessions and cookies are essential for maintaining state in web applications. Interviewers will test your understanding of these concepts, as they are used for tasks like user authentication and shopping carts.

• Sessions: A session is a server-side mechanism to store user data across multiple pages. The session ID is stored on the client-side in a cookie, but the session data itself is stored on the server.

• Cookies: A cookie is a small piece of data stored on the client-side in the browser. Cookies are often used to store user preferences or session data that persists across sessions.

You should explain when to use sessions (for sensitive data) and cookies (for persistent, non-sensitive data).

5. What Is the Difference Between POST and GET Methods in PHP?

Understanding HTTP methods is crucial for web development. POST and GET are two commonly used methods for submitting data in PHP.

• GET: Sends data via the URL, making it visible in the browser’s address bar. It is best used for retrieving data or submitting non-sensitive information.

• POST: Sends data in the HTTP request body, making it invisible to the user. It is used for submitting sensitive data (like passwords) or large amounts of data.

You should also mention that POST is more secure than GET because it does not expose the data in the URL.

6. What Are PHP Arrays, and How Are They Used?

Arrays are one of the most common data structures used in PHP. Interviewers will want to know how well you understand arrays and their various uses.

• Indexed Arrays: Arrays with numeric indices.

• Associative Arrays: Arrays with named keys, allowing you to store key-value pairs.

• Multidimensional Arrays: Arrays containing other arrays, used for complex data storage.

Example of an associative array:

php

$student = array("name" => "John", "age" => 20, "grade" => "A");

You should also explain how to access, modify, and loop through arrays in PHP.

7. What Are PHP Superglobals?

PHP Superglobals are built-in global arrays that are always accessible, regardless of scope. Interviewers may ask about your knowledge of these superglobals.

Common PHP superglobals include:

• $_GET: Used to collect form data sent via the GET method.

• $_POST: Used to collect form data sent via the POST method.

• $_SESSION: Used to store session variables.

• $_COOKIE: Used to store cookies.

• $_FILES: Used to handle file uploads.

• $_SERVER: Contains information about the server environment and request headers.

8. What Is PDO in PHP?

PDO (PHP Data Objects) is a database access layer that provides a uniform interface for interacting with different types of databases. Interviewers often ask about PDO to test your database interaction skills.

PDO offers several advantages:

• Database Independence: PDO allows you to switch between different database systems (e.g., MySQL, PostgreSQL) without changing the code.

• Prepared Statements: PDO supports prepared statements, which help prevent SQL injection attacks by separating SQL logic from the data.

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

Understanding comparison operators is crucial in PHP. The difference between == and === is a common interview question.

• ==: The equality operator checks if two values are equal, after type juggling (e.g., 0 == "0" is true).

• ===: The identity operator checks if two values are equal and of the same type (e.g., 0 === "0" is false).

This distinction helps you avoid type conversion issues when comparing values in PHP.

10. How Do You Handle Errors in PHP?

Error handling is an important aspect of writing robust PHP applications. Interviewers may ask about your approach to handling different types of errors in PHP.

PHP supports several error handling mechanisms:

• Error Reporting: You can use error_reporting() to specify which errors to report.

• try-catch: Used for handling exceptions in modern PHP.

• Custom Error Handlers: You can create custom error handling functions using set_error_handler().

11. What Are Namespaces in PHP?

Namespaces in PHP help avoid name conflicts when working with large applications or libraries. Interviewers may ask about the use of namespaces, especially in modern PHP applications.

You can define a namespace at the beginning of a file and refer to it using the use keyword:

php

namespace MyApp; class User { ... } use MyApp\User;

Namespaces help organize code and prevent function or class name collisions in larger projects.

Conclusion

PHP remains a powerful and versatile language for web development, powering everything from dynamic websites to complex content management systems. By preparing for these top PHP interview questions, you’ll be well-equipped to tackle PHP developer interviews in 2025 and beyond.

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