What’s in a PHP programmer technical interview or test?

PHP remains a dominant backend programming language, still widely used in 2025 for web development, CMS platforms, and enterprise applications.

If you're preparing for a PHP technical interview, it's essential to be ready for a range of questions covering fundamental concepts, coding exercises, and problem-solving skills.

Here, exclusively for Free-Work, is an overview of key areas and sample questions you may encounter in a PHP programmer technical interview, so you can be prepared, writes Ben Quinn, head of technology recruitment at Leap 29.

1. Core PHP concept interview openers

Interviewers often begin by assessing your foundational knowledge of PHP. Five likely questions, or their variants, therefore are:

1. What are the differences between echo, print, and printf in PHP?

2. How does PHP handle variable scope?

3. What are superglobals in PHP?

4. Explain the difference between == and === operators in PHP.

5. How does type juggling work in PHP?

2. Object-Oriented PHP

Many modern applications use OOP principles in PHP.

So you might hear at your interview, or be asked in a technical test:

• Explain the four pillars of Object-Oriented Programming: Encapsulation, Inheritance, Abstraction, and Polymorphism.

• How do you create and extend a PHP class?

• What is the difference between an abstract class and an interface?

• What is method overriding and method overloading in PHP?

• Explain the use of traits in PHP.

3. Database and SQL knowledge

A strong understanding of database integration is crucial for PHP developers whether you’re ‘going forward’ for a contract (as a freelance or temporary worker) or ‘applying’ for a position (as a full-time or permanent employee).

It’s prudent to expect these five as a minimum:

1. How do you connect to a MySQL database using PHP?

2. What is the difference between MySQLi and PDO?

3. How do you prevent SQL injection in PHP?

4. What is an ORM, and have you used one in PHP?

5. Explain the ACID properties in the context of databases.

4. Security best-practices

PHP developers should be aware of security vulnerabilities and how to mitigate them.

To gauge that security know-how, PHP job interviewers or PHP technical examiners often ask:

• What are common PHP security threats, and how do you prevent them?

• How do you prevent Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF)?

• What are prepared statements, and why should you use them?

• How do you securely hash passwords in PHP?

• What is the difference between include, require, include_once, and require_once?

5. PHP frameworks: Laravel, Symfony, CodeIgniter

If the PHP role on offer requires framework experience, be ready to answer questions in and around these five:

1. What are the key features of Laravel?

2. Explain routing and middleware in Laravel.

3. What is dependency injection in Symfony?

4. How does CodeIgniter handle MVC architecture?

5. What are service providers in Laravel?

6. Testing and debugging in PHP

A good PHP developer should know how to test and debug applications effectively.

The queries routinely fired to ascertain knowledge here centre on:

• What are the different error reporting levels in PHP?

• How do you enable error logging in PHP?

• What tools do you use for debugging PHP code?

• Have you worked with PHPUnit? Explain its importance.

• How do you handle exceptions in PHP?

7. Coding challenges and algorithmic questions

You’ll typically be briefed or warned by your recruitment agency in advance but broadly speaking, PHP job candidates should expect to write and optimise PHP code during a live coding session.

The most likely commands or prompts are these four:

1. Write a function to check if a string is a palindrome.

2. Implement a function to find the second-highest number in an array.

3. Write a script to fetch data from an API and store it in a database.

4. Optimise a given PHP loop for better performance.

8. Version control and deployment

Modern PHP developers should understand version control and deployment strategies.

This quartet shouldn’t therefore faze you if you're up-to-date, but it is likely to be posed:

• How do you use Git in a PHP project?

• What is CI/CD, and how have you implemented it in a PHP application?

• How do you deploy a PHP application to a production server?

• What are some performance optimisation techniques in PHP applications?

PHP interview questions and test: wrap up

A PHP technical interview or test can cover a wide range of topics, from basic syntax to complex architectural questions. The almost 40 questions above are common in PHP job interviews.

Preparing in advance with hands-on coding practice, reviewing key concepts, and understanding modern development workflows will give you the confidence needed to succeed. Try to keep a harmonious balance throughout, focusing on both theoretical knowledge and practical implementation to really demonstrate your expertise as a PHP developer.