Important Topics Every PHP Developer Must Learn for Interviews (2025 Guide)

Hey there, future PHP Developer! 👋

Are you preparing for PHP developer interviews and feeling a bit overwhelmed? Don’t worry! In this blog, we’ll break down the most important topics you should focus on to crack PHP interviews with confidence.

Whether you're applying for your first job or want to upgrade your skills, this guide is your cheat sheet. Let’s dive in!

🧭 Why Prepare for PHP Interviews the Right Way?

PHP is still one of the most popular server-side languages in 2025, with millions of websites and applications relying on it.
But in interviews, companies look for more than just syntax knowledge. They want:
✅ Solid understanding of core concepts
✅ Practical problem-solving skills
✅ Awareness of best practices and security
✅ Ability to write clean, efficient code

🧠 Top Topics to Master for PHP Interviews

Here’s a clear roadmap of what to study:

1️⃣ Core PHP Concepts

These are the basics you must know:

• Variables and Data Types (string, integer, array, etc.)
• Operators (arithmetic, logical, comparison)
• Control Structures (if, else, switch)
• Loops (for, while, foreach)
• Functions (declaration, arguments, return values)
• Scope (Global, Local, Static)

Example Question:

What is the difference between == and === in PHP?

2️⃣ Arrays and String Functions

Arrays are fundamental in PHP:

• Indexed, Associative, and Multidimensional Arrays
• Array functions like array_merge(), array_diff(), array_map()
• String functions like strlen(), strpos(), str_replace(), substr()

Example Question:

How do you remove duplicate values from an array in PHP?

3️⃣ Superglobals in PHP

Understand the global variables like:

• $_GET, $_POST, $_REQUEST
• $_SESSION, $_COOKIE
• $_SERVER, $_FILES

Know how to use these in form handling and data processing.

Example Question:

What is the difference between $_POST and $_REQUEST?

4️⃣ Working with Forms and File Handling

• How to process HTML forms in PHP
• How to upload files using $_FILES
• How to validate and sanitize form inputs

Example Question:

How would you handle a file upload securely in PHP?

5️⃣ Database Integration (MySQL with PHP)

This is a must-know area:

• Connecting to a database (mysqli or PDO)
• CRUD Operations: Create, Read, Update, Delete
• Prepared Statements (for security)
• Basic SQL Queries

Example Question:

How do you prevent SQL injection in PHP?

6️⃣ Object-Oriented Programming (OOP) in PHP

Many companies prefer OOP in PHP. Focus on:

• Classes and Objects
• Properties and Methods
• Inheritance
• Interfaces & Abstract Classes
• Traits
• Namespaces

Example Question:

What is the difference between an abstract class and an interface in PHP?

7️⃣ Error Handling and Exceptions

Understand:

• try...catch blocks
• throw keyword
• Custom exception handling

Example Question:

How does exception handling improve code quality?

8️⃣ Security Best Practices

Very important for interviews!

• SQL Injection (and how to prevent it)
• XSS (Cross-Site Scripting)
• CSRF (Cross-Site Request Forgery)
• Password Hashing (password_hash(), password_verify())
• Using HTTPS

Example Question:

Why is it important to use password_hash() instead of md5() for passwords?

9️⃣ PHP Frameworks (Laravel Basics)

Many companies use Laravel. Be prepared to answer:

• What is MVC architecture?
• How do routes work in Laravel?
• What is migration, seeding, and artisan commands?
• Laravel features like Eloquent ORM, middleware, authentication, and validation.

Example Question:

What is the difference between hasOne and belongsTo relationships in Laravel?

🔥 Bonus Topics (For Advanced Roles)

For mid-level or senior roles, explore:

• Composer (dependency management)
• APIs (REST, JSON handling)
• Testing (PHPUnit basics)
• Docker basics (optional but impressive)
• Version Control (Git, GitHub)

📝 Quick Revision Checklist

Here’s a handy checklist before your interview:

✅ Core PHP Concepts
✅ Arrays & Strings
✅ Superglobals
✅ Forms & File Handling
✅ MySQL + PHP (CRUD + SQL)
✅ OOP in PHP
✅ Error Handling
✅ Security
✅ Laravel Basics
✅ Bonus: Composer, APIs, Git

💡 Final Tips for Interview Success

🌟 Practice Coding – Build small projects and solve problems.
🌟 Understand Concepts, Not Just Syntax – Think why, not just how.
🌟 Be Ready for Practical Questions – They may ask you to write code!
🌟 Stay Updated – Follow PHP community news and best practices.

🚀 You Can Do This!

Interviews are a stepping stone, not a wall.
With preparation, practice, and a positive mindset, you’ll be ready to crack your PHP interview and start your career confidently.

You’ve got this! 💪💙