PHP Developer Interview Questions UK: 8 Real Questions and What Interviewers Want

Before your PHP Developer interview, it helps to see the questions from the interviewer's side. We have picked eight from our set of 16 and added the reason each one gets asked.

Eight PHP Developer interview questions, and what the interviewer is thinking

1. What are the main differences between PHP 7 and PHP 8, and which newer language features do you use regularly?

Why they ask: It checks whether your PHP knowledge is modern rather than stuck on legacy versions.

2. How do you prevent SQL injection, XSS and CSRF in a PHP application?

Why they ask: Security is a basic expectation, and PHP applications are frequent targets.

3. Can you explain how Composer and PSR standards help structure a modern PHP project?

Why they ask: Tooling and standards knowledge shows professional PHP practice.

4. Compare Laravel and Symfony. How would you choose between them, and what core features of Laravel do you use?

Why they ask: Framework choice is a frequent discussion, and most UK PHP roles involve one of them.

5. How do you diagnose and improve the performance of a slow PHP application?

Why they ask: Performance tuning across code, database and infrastructure is a common PHP task.

6. A client reports that their PHP website has been hacked and is serving spam links. What do you do?

Why they ask: It tests incident response and security thinking under pressure.

7. Tell me about a time you built or improved an important feature in a PHP application.

Why they ask: They want a concrete example of delivery with outcomes.

8. Why do you want to work as a PHP developer, and where do you see the language heading?

Why they ask: It tests motivation and awareness of PHP's current state, beyond old stereotypes.

A sample answer to question 1

What are the main differences between PHP 7 and PHP 8, and which newer language features do you use regularly?

PHP 7 brought major performance gains, scalar type declarations and return types. PHP 8 added named arguments, union types, the match expression, constructor property promotion, the nullsafe operator, attributes and the JIT compiler, and PHP 8.1 introduced enums, readonly properties and first-class callable syntax, with 8.2 and later adding readonly classes and further typing refinements. I use constructor promotion and readonly properties to cut boilerplate, enums instead of string constants, match instead of verbose switch statements, and strict types declared at the top of files so type juggling doesn't cause surprises. I run static analysis with PHPStan or Psalm at a high level, and Rector to automate upgrades. It matters to stay on a supported version, because old releases stop receiving security fixes, so I plan upgrades regularly and check framework and package compatibility with Composer before changing the runtime.

Common mistake to avoid: Describing only PHP 5 style code; ignoring end-of-life security risk

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the PHP Developer interview questions page. The first five are free, no sign-up needed.