Fundamentals

1. What is PHP?

   • PHP is a server-side scripting language primarily used for web development. It's known for its simplicity, ease of use, and large community support.

2. What are the key features of PHP?

   • Open-source: Free to use and distribute.
   • Platform-independent: Runs on various operating systems.
   • Large community: Extensive documentation, frameworks, and libraries available.
   • Database connectivity: Easy integration with databases like MySQL, PostgreSQL, etc.
   • Object-Oriented Programming (OOP): Supports OOP concepts like classes, objects, inheritance, polymorphism.

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

   • == (loose comparison): Checks for equality of values, but may perform type conversion.
   • === (strict comparison): Checks for both equality of values and data types.

4. What are the different data types in PHP?

   • Integer, float, string, boolean, array, object, null, resource.

5. What is the purpose of the $this keyword in PHP?

   • Refers to the current object within a class method.

Control Structures

6. Explain the use of if, else if, and else statements in PHP.

   • Used for conditional execution of code based on certain conditions.

7. What are loops in PHP?

   • for, while, do-while, foreach - used to repeat a block of code multiple times.

8. How do you handle errors in PHP?

   • try-catch blocks for exception handling.
   • error_reporting() function to control error reporting levels.

Functions

9. What is a function in PHP?

   • A block of code that performs a specific task and can be reused.

10. What are function arguments and return values?

• Arguments are values passed to a function.
• Return values are the output of a function.

Arrays

11. How do you create an array in PHP?

• Using array() constructor or short array syntax [].

12. What are the different types of arrays in PHP?

• Indexed arrays, associative arrays, multidimensional arrays.

13. How do you access elements in an array?

• Using array indices.

Strings

14. How do you manipulate strings in PHP?

• Using built-in string functions like strlen(), strpos(), substr(), str_replace().

15. What are string interpolation and concatenation?

• Interpolation: Embedding variables directly within a string using double quotes.
• Concatenation: Joining two or more strings together using the . operator.

Object-Oriented Programming (OOP)

16. What are classes and objects in PHP?

• Classes: Blueprints for creating objects.
• Objects: Instances of a class.

17. Explain the concepts of inheritance and polymorphism in PHP.

• Inheritance: A class inherits properties and methods from a parent class.
• Polymorphism: Objects of different classes can be treated as objects of a common type.

18. What are access modifiers in PHP?

• public, protected, private - control the visibility of class members.

Databases

19. How do you connect to a MySQL database in PHP?

• Using the mysqli or PDO extensions.

20. Explain the concept of SQL injection and how to prevent it.

• SQL injection is a security vulnerability where malicious SQL code is injected into an application.
• Prevent it using prepared statements and parameterized queries.

File Handling

21. How do you read and write files in PHP?

• Using functions like fopen(), fread(), fwrite(), fclose().

Sessions and Cookies

22. What are sessions in PHP?

• Server-side mechanism to store user data across multiple pages.

23. What are cookies in PHP?

• Small pieces of data stored on the client-side (browser).

Regular Expressions

24. What are regular expressions in PHP?

• Patterns used to match and manipulate text.

Error Handling

25. What are the different types of errors in PHP?

• Syntax errors, runtime errors, logical errors.

Security

26. Explain the importance of input validation in PHP.

• To prevent security vulnerabilities like SQL injection and cross-site scripting (XSS).

27. What are some common security measures in PHP?

• Using prepared statements, escaping user input, filtering data, regular expressions for input validation.

Frameworks

28. What are PHP frameworks?

• Pre-built libraries and tools that provide a structure for web application development.

29. Name some popular PHP frameworks.

• Laravel, Symfony, CodeIgniter, Zend Framework.

Advanced Topics

30. Explain the concept of namespaces in PHP.

• Organize code by grouping related classes and interfaces under a unique name.

31. What are interfaces in PHP?

• Define a contract that classes must adhere to.

32. What are traits in PHP?

• A mechanism for code reuse across different classes without using inheritance.

Data Structures

33. Implement a stack in PHP.

• Use an array to represent the stack.

34. Implement a queue in PHP.

• Use an array or a linked list.

Algorithms

35. Implement a bubble sort algorithm in PHP.

36. Implement a binary search algorithm in PHP.

Design Patterns

37. Explain the Singleton design pattern in PHP.

• Ensures that only one instance of a class exists.

38. Explain the Observer design pattern in PHP.

• Defines a one-to-many dependency between objects, so when one object changes state, all its dependents are notified and updated automatically. ¹  
  1. www.codeinbits.com

  www.codeinbits.com

Testing

39. What is unit testing in PHP?

• Testing individual units of code (e.g., functions, classes) in isolation.

40. How do you write unit tests in PHP?

• Using frameworks like PHPUnit.

Performance Optimization

41. How can you improve the performance of a PHP application?

• Caching, database optimization, code profiling, using efficient algorithms.

Networking

42. How do you make HTTP requests in PHP?

• Using functions like file_get_contents(), cURL.

Security

43. Explain the concept of cross-site scripting (XSS) and how to prevent it.

• XSS attacks inject malicious scripts into web pages.
• Prevent it by escaping user input, using output encoding, and input validation.

44. Explain the concept of cross-site request forgery (CSRF) and how to prevent it.

• CSRF attacks trick users into performing actions on a website they don't intend to.
• Prevent it using CSRF tokens, verifying HTTP Referer headers.

Frameworks

45. What are the advantages of using a PHP framework?

• Improved code organization, reusability, security, and maintainability.

46. Explain the concept of routing in PHP frameworks.

• Mapping incoming HTTP requests to specific controllers and actions.

Advanced Topics

47. What is dependency injection in PHP?

• A design pattern where objects are given their dependencies instead of creating them themselves.

48. Explain the concept of composer in PHP.

• A dependency management tool for PHP.

49. What are PHP extensions?

• Modules that extend the functionality of PHP.

50. How do you handle large datasets in PHP?

• Using pagination, caching, and database optimization techniques.

I hope these questions are helpful for your interview preparation! Let me know if you have any other questions.