Examples of PHP Interview Questions

Godwin Oluponmile
Godwin Oluponmile
Published: 19.09.2022

If you're looking to hire a senior developer, or you want to get hired as one, the following questions will help you ace the interview. Many PHP interview questions senior developers assume aren't what recruiters use.

More than 77% of the 1.8 billion websites in the entire universe survive on PHP. There's a surge in demand for senior PHP developers, and PHP is reportedly one of the top five sought-after programming languages today. You might want to further your career or get a better job by applying as a senior developer.

You are likely unsure of what to expect from the job interview. Today I'll elaborate on what PHP is about and essential interview questions you should know.

What is PHP?

A laptop on a desk with programming codes on the screen. PHP is written boldly on the image

The full meaning of PHP is Hypertext Preprocessor, formerly known as Personal Home Page. PHP is an open-source scripting language that serves general purposes, from designing a static or dynamic website to a web application. It is easy to use, fast and flexible, unlike most high-end languages used in web development.

At the moment, more than 20 million domains make use of PHP as their scripting language. It is the main language used on Facebook and sites such as Wikipedia and WordPress.

Why is PHP Widely Used?

Over the years, PHP has dominated the world of web development, which is why even anyone with no prior knowledge of web development is advised to learn it as a start.

Newbies find it user-friendly, even though it has more advanced features for experienced developers. Within a short period, you can easily comprehend the fundamentals of PHP and begin to write simple scripts.

PHP is free to use, easy to learn, and runs efficiently on most web servers. It also functions on major operating systems such as Mac OS, Windows, and Linux. Other added technical benefits of using PHP have made it preferred by many developers today. They include:

  • Platform-independence
  • Open source
  • Syncing with other databases
  • Supportive online community

Basic Concepts a Senior Developer Should Know About PHP

A group of four developers

You are here for the interview questions, but these PHP concepts will aid your interview process - they form the basis of most interview questions. Before you take that interview, you may want to review these fundamental concepts:

The PHP Language

The first is to learn how to read and speak fluent PHP. This will help you write codes and differentiate between good and wrong source files.

For instance, the PHP code language is written enclosed in special start () tags for processing instructions that help you jump into and out of "PHP mode.”

So, the code sample returns “I love programming!” when executed as:

$txt = "programming";

echo "I love $txt!";


The PHP Framework

Several PHP frameworks such as Laravel, CodeIgniter, and Symfony simplify the web development process. Learning, mastering, and using this framework will not only help improve your skill in web development but will make your work appear more professional.

PHP Core Functions

Unraveling the different functions used in PHP isn't sufficient enough. Figuring out when to use which function to achieve what result is also reasonable. Although you have the option to create your personalized functions, it is still best if you know ready-made functions that would perform the same operation you want to complete. It will save you some time.

Right Source Editor

Knowing the right editor for your work is crucial as a senior developer. This will aid speed, smartness, and accuracy while you work. When choosing an editor, you want to ensure you use the one with in-built debugging tools that'll help you navigate a code and highlight syntax.

Configuration Files

Knowing how to create configuration files sets you aside as distinct amidst others. A rich understanding helps you organize your database connections professionally. You want to make your PHP coding easier to manage and integrate, hence the need to dig deeper into the hacks of configuration files.

Code Snippets

A decent knowledge of code snippets is also important for a senior developer. Then selecting your favorite code snippets and ensuring they are always ready to use is smart. They will not only help save time, but they will also make writing PHP codes easier for you.

After you have exhausted days or even weeks learning the basics of PHP, a little brush-up before your big day to guide you as you prepare for the interview is not a bad idea.

Below are 50 crucial questions in no particular order that will guide your preparation:

1. What is the difference between == and ===?

2. What are the differences between “echo” and “print” in PHP?

3. What are “Traits” in PHP?

4. What does “PEAR” mean?

5. What does the header ( ) function use in PHP?

6. How can you tell if a number is even or odd without using any condition or loop?

7. What is the difference between a “session” and “cookies”?

8. What is the difference between the include ( ) and require ( ) functions?

9. How can you get the IP address of a client?

10. What is the difference between unset ( ) and unlink ( )?

11. What are the main error types in PHP, and what are their differences?

12. How does unit testing work in PHP?

13. What is the difference between GET and POST methods?

14. How can you enable error reporting in PHP?

15.What are the __construct ( ) and __destruct ( ) methods in a PHP class?

16. What are the types of arrays in PHP?

17. How can you get the number of elements in an array?

18. What are the three scope levels available in PHP, and what do they mean?

19. What do getters and setters mean, and what is their importance?

20. What does MVC mean, and what does each component do?

21. What are SQL injections, and how are they prevented?

22. Why should you use === instead of ==?

23. What do PSRs mean, and briefly describe one of them.

24. What are the PSR standards that should be followed?

25. What is the difference between MySQL_ functions and PDO?

26. How does inheritance work with PHP?

27. Can you support multiple inheritances in PHP?

28. How can you pass a variable by reference?

29. How are exceptions handled in PHP?

30. Are objects passed by value or by reference in PHP?

31. What is the difference between const and define?

32. What does PDO mean, and what is it used for?

33. When should you use require and include?

34. What is the difference between exception and error?

35. What are the differences between parameterized functions and non-parameterized functions?

36. How are variables and data passed from PHP to JavaScript?

37. What function is used to make a copy of a PHP array?

38. Mention some exception class functions.

39. What is the use of a Null Coalesce Operator?

40. What does extract ( ) mean?

41. What is Type hinting in PHP?

42. What are late static bindings in PHP?

43. How do you merge two PHP objects?

44. How can you implement method overloading in PHP?

45. How can a database be created using PHP and MySQL?

46. What do overloading and overriding mean in PHP?

47. How can you connect to URL, MySQL, and JavaScript in PHP?

48. What is the use of callback in PHP?

49. How can you upload a file using PHP?

50. How can you encrypt a password using PHP?

Roles of a Senior Developer with Knowledge of PHP

Have you ever wondered what differentiates a senior developer from a junior one? There are no specific job descriptions for either party; it entirely depends on the company hiring and what is expected from each employee.

What sets them apart is the job requirements and level of experience. Some of the responsibilities include:

  • Active participation in design and code reviews, testing units, and fixing defects.
  • Developing and conducting workshops and training
  • Designing and developing large, complex modules and components of larger system designs.
  • Source control, developing bug tracking systems, continuous integration, and packaging.
  • Designing and implementing integrations between games and other social networks using PHP.

Generally, asides from the usual development of software, senior developers have more duties to carry out in terms of leadership and management of teams of PHP developers. Mentoring junior developers, too, can be part of their job description.

In Summary

You don't need the A-Z knowledge of PHP before getting hired as a senior developer. PHP allows you to learn on the job. The more you use it, the better you become at using it. Just ensure you have the basic knowledge of the basic concepts b in the scripting language, and you can ace that interview.


Q1. What questions should I ask a senior developer?

  • Describe one of your previous favorite projects and how you approached it.
  • What programming languages do you use the most?,
  • How do you test and find a bug in an application?
  • What can you do when an application stops working?
  • What are the biggest challenges of working on the front end of an application?
  • What are your preferred content management systems?
  • What is your experience with SQL?
  • How do you organize class modules and assets?
  • Do you have experience working with object-oriented programming (OOP)?

Q2. What are the questions asked for the interview about PHP?

  • What is PHP?
  • What are the common PHP functions?
  • What is PEAR in PHP?
  • What was PHP formerly known as?
  • What is the difference between static and dynamic websites?
  • Is PHP a case-sensitive language?
  • What are the rules for naming a PHP variable?
  • How do you define a constant in PHP?

Q3. Why is Echo used in PHP?

Because Echo acts more as a language construct than a function, it is used to display the output of one or more strings, numbers, or variables from parameters passed to it. It is relatively faster than other alternatives and is quite easy to understand, making it the most usable command in PHP.

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