Interviewing PHP developers is not just about syntax or framework knowledge. The real challenge is identifying candidates who understand backend fundamentals, real-world application design, performance, and maintainability, especially in environments where PHP often powers business-critical systems.
This guide provides a comprehensive and structured list of PHP interview questions and answers, categorized by experience level and specialization, helping you evaluate candidates consistently and confidently.
Who This Guide Is For
- Hiring managers and founders building backend teams
- Tech leads conducting technical interviews
- Recruiters screening PHP developers
- Companies maintaining or modernizing PHP-based systems
How This Guide Was Built
We analyzed and benchmarked content from top-ranking sources such as:
- GeeksForGeeks
- InterviewBit
- Turing
- BuiltIn
- Indeed Career Guide
- Simplilearn
- FreeCodeCamp
- W3Schools
- HackerRank
- Various agency and framework-specific blogs
Most existing resources either:
- Focus too much on theory
- Lack of senior-level depth
- Ignore real production scenarios
This guide fixes those gaps.
1. Junior PHP Developer Interview Questions
These questions assess fundamental PHP knowledge, basic backend concepts, and learning potential.
1. What is PHP, and what is it commonly used for?
Answer:
PHP is a server-side scripting language primarily used for building dynamic web applications. It handles backend logic such as form processing, database interaction, authentication, and API development.
2. What is the difference between echo and print?
Answer:
Both output data to the browser, but echo is faster and does not return a value, while print returns 1 and can be used in expressions.
3. Explain the difference between GET and POST.
Answer:
- GET sends data via URL parameters and is visible and cacheable.
- POST sends data in the request body and is more secure for sensitive data.
4. What are PHP variables and how are they declared?
Answer:
Variables in PHP start with $ and do not require explicit data types. PHP is loosely typed.
5. What are sessions and cookies?
Answer:
Cookies store data on the client side, while sessions store data on the server and are commonly used for authentication and user state.
6. What is the difference between include and require?
Answer:
include throws a warning if a file is missing; require throws a fatal error and stops execution.
7. What are arrays in PHP?
Answer:
Arrays store multiple values in a single variable and can be indexed, associative, or multidimensional.
8. What is basic error handling in PHP?
Answer:
Using try-catch, error reporting levels, and custom error handlers.
2. Mid-Level PHP Developer Interview Questions
These questions focus on framework usage, architecture, performance, and integration skills.
1. What is MVC architecture, and why is it important?
Answer:
MVC separates business logic (Model), presentation (View), and control flow (Controller), improving maintainability and scalability.
2. Explain how Laravel works at a high level.
Answer:
Laravel uses MVC architecture, routing, middleware, service containers, and ORM (Eloquent) to simplify PHP application development.
3. What is Composer, and why is it important?
Answer:
Composer is PHP’s dependency manager, allowing developers to manage libraries, versions, and autoloading efficiently.
4. How do you prevent SQL injection in PHP?
Answer:
By using prepared statements, parameter binding, ORM tools, and input validation.
5. What is the difference between == and === in PHP?
Answer:
== compares values loosely, while === compares both value and type strictly.
6. Explain RESTful APIs in PHP.
Answer:
REST APIs use HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations, often returning JSON responses.
7. What is middleware in Laravel?
Answer:
Middleware filters HTTP requests before they reach controllers, commonly used for authentication, logging, and access control.
8. How do you handle file uploads securely in PHP?
Answer:
Validate file types, limit size, sanitize filenames, and store files outside the public directory when possible.
9. What is caching, and how is it implemented in PHP?
Answer:
Caching stores frequently accessed data in memory (Redis, Memcached) to reduce database load and improve performance.
3. Senior PHP Developer Interview Questions
Senior-level questions evaluate architecture, scalability, performance optimization, and leadership mindset.
1. How would you design a scalable PHP application?
Answer:
By separating concerns, using caching layers, optimizing database queries, implementing queues, and leveraging load balancers.
2. How do you handle legacy PHP codebases?
Answer:
Gradually refactor, add tests, isolate risky components, improve documentation, and modernize incrementally.
3. Explain dependency injection and service containers.
Answer:
Dependency injection reduces tight coupling. Service containers manage object creation and lifecycle automatically.
4. How do you optimize PHP application performance?
Answer:
- Query optimization
- Caching
- Opcode caching (OPcache)
- Reducing I/O operations
- Profiling with tools like Xdebug or Blackfire
5. How do you secure a PHP application?
Answer:
By preventing XSS, CSRF, SQL injection, using HTTPS, validating inputs, hashing passwords, and applying least-privilege principles.
6. Explain queues and background jobs in Laravel.
Answer:
Queues handle time-consuming tasks asynchronously, improving request-response performance.
7. What are the PHP design patterns you commonly use?
Answer:
Factory, Repository, Singleton (with caution), Strategy, Observer.
8. How do you mentor junior developers?
Answer:
Through code reviews, pairing, documentation, and setting clear engineering standards.
4. PHP Framework & Ecosystem Questions
- Laravel vs Symfony; when to use each?
- What is Eloquent ORM and its pros/cons?
- How does Laravel’s request lifecycle work?
- What are migrations and seeders?
- How do you version APIs in PHP?
5. Database & Backend Integration Questions
- How do you optimize slow MySQL queries?
- Explain indexing and normalization
- When would you use Redis over MySQL?
- How do you handle database transactions?
6. Behavioural & Team-Fit Questions
- Describe a challenging PHP bug you fixed
- How do you keep up with PHP updates?
- Tell us about a time you refactored messy code
- How do you handle production incidents?
7. PHP Coding Challenges (Interview Use)
Easy
- Reverse a string
- Count array values
- Validate email format
Medium
- Build a basic CRUD API
- Implement pagination
- Upload and validate files
Hard
- Design a rate-limiting system
- Build a queue-based email sender
- Refactor a legacy PHP script
Final Notes for Interviewers
A good PHP interview should balance:
- Fundamentals
- Framework knowledge
- Real-world problem solving
- Communication and ownership
Strong PHP developers are often undervalued, but in the right system, they are critical to long-term product stability.
If you’re ready to move from interviewing to hiring, you can work with pre-vetted PHP developers through Tech for Hire and skip the long screening cycle:
Frequently Asked Questions
- What level of PHP knowledge should I expect from a junior developer?
- Basic PHP syntax, understanding of forms, sessions, databases, and a willingness to learn frameworks.
- Are Laravel interview questions mandatory for PHP roles?
- For most modern projects, yes. Laravel is widely used and reflects real production environments.
- How many interview rounds are ideal for PHP developers?
- Typically 2–3 rounds: technical basics, practical problem-solving, and team fit.
- Should PHP developers know frontend technologies?
- Basic knowledge helps, but it’s not mandatory unless the role is full-stack.
- How do I assess real-world PHP experience?
- Ask about past projects, performance challenges, security issues, and how problems were solved in production.