Comprehensive PHP Interview Questions (Practical Experience)

This article compiles a thorough list of PHP interview questions covering object‑oriented concepts, session and cookie differences, HTTP status codes, data types, storage engines, functions, security, performance, and various advanced topics to help candidates prepare effectively.

1. What is object‑oriented? What are its main features?

2. What is the difference between SESSION and COOKIE? Explain from the protocol, the reasons they exist, and their functions.

3. What do the HTTP status codes 302, 403, and 500 mean?

4. Explain the meanings of the data types (int, char, varchar, datetime, text) and the difference between varchar and char.

5. What are the basic differences between MyISAM and InnoDB? How are their index structures implemented?

6. What is the difference between isset() and empty() ?

7. Explain the difference between passing by value and passing by reference in PHP. When should each be used?

8. What does the error_reporting function do in PHP?

9. Describe your understanding of caching technologies.

10. What are the three layers of the MVC architecture and what are its advantages?

11. What are the advantages of AJAX?

12. How can program execution efficiency be improved during development?

13. For high‑traffic websites, what methods do you use to handle large visitor volumes?

14. What is the difference between include and require ? Which statement can replace them to avoid multiple inclusions?

15. What is the difference between foo() and @foo() ?

16. Briefly describe PHP's garbage collection mechanism.

17. How can PHP security be maximized? How to prevent SQL injection and XSS attacks?

18. What are the differences among echo , print_r , print , and var_dump ?

19. What are the characteristics of the Smarty template engine?

20. How to implement page redirection in PHP?

21. How to convert a GB2312‑encoded string to UTF‑8?

22. Which function should be used to output user‑provided content verbatim before storing it in the database?

23. What are CSRF and XSS attacks, and how can they be prevented?

24. What security mechanisms are essential to consider during development?

25. What is your understanding of the JSON data format?

26. What is a transaction and what are its properties?

27. What is a lock in database systems?

28. What is the purpose of indexes, and what are their advantages and disadvantages?

29. Explain the three normal forms in simple terms.

30. What are the differences between primary keys, foreign keys, and indexes?

31. Describe the access permissions of private , protected , and public modifiers.

32. What is the difference between heap and stack memory?

33. What are the common magic methods in PHP? Provide examples.

34. What do $this , self , and parent represent, and when should each be used?

35. How is the scope resolution operator :: used and in what scenarios?

36. How does the __autoload() method work?

37. Briefly describe solutions for high‑concurrency website scenarios.

38. How to traverse all files in a directory using PHP?

39. How to run PHP programs from the command line?

40. Which methods do you use to check PHP script execution time and database query performance, and how do you locate bottlenecks?

41. How to handle page view statistics for high‑traffic sites?

42. How to optimize a MySQL database that stores over 50,000 daily increments for a publishing system over three years?

43. Differences between MyISAM and InnoDB storage engines.

Additional personal insights after interviews include advice on scheduling interviews, selecting companies, maintaining mindset, and understanding that offers can involve luck.