Here are interview questions on technical skills related to PHP Developer Jobs in the USA;

1. Question: Can you explain the difference between PHP 5 and PHP 7?

   • Answer: PHP 7 introduced several improvements over PHP 5, including better performance, scalar type declarations, return type declarations, the spaceship operator (<=>), and the introduction of the null coalescing operator (??).

2. Question: What are traits in PHP, and how are they used?

   • Answer: Traits are a mechanism for code reuse in single inheritance languages. They allow a developer to reuse a set of methods in several independent classes. You use the use keyword to include a trait in a class.

3. Question: Explain the purpose of Composer in PHP development.

   • Answer: Composer is a dependency manager for PHP that simplifies the process of managing external libraries and packages. It allows for easy installation, updating, and autoloading of libraries into your project.

4. Question: How does autoloading work in PHP, and why is it beneficial?

   • Answer: Autoloading is the process of automatically including the required class files without the need for explicit require or include statements. PSR-4 autoloading, supported by Composer, is a widely used standard in PHP that enhances code maintainability and organization.

5. Question: Explain the use of PDO in PHP and why it is preferred for database interactions.

   • Answer: PDO (PHP Data Objects) is a database access layer providing a uniform method of access to multiple databases. It is preferred for its security benefits, as it supports prepared statements, preventing SQL injection attacks.

6. Question: What is the purpose of the use keyword in PHP namespaces?

   • Answer: The use keyword in PHP namespaces is used to import namespaces into the current scope. It allows you to reference classes or functions from a different namespace without the need to fully qualify their names.

7. Question: How can you prevent SQL injection in PHP?

   • Answer: SQL injection can be prevented by using prepared statements and parameterized queries. This ensures that user input is treated as data rather than executable code.

8. Question: Explain the concept of MVC architecture in PHP.

   • Answer: MVC (Model-View-Controller) is an architectural pattern that separates an application into three main components: the Model (data and business logic), the View (presentation and user interface), and the Controller (handles user input and updates the model and view accordingly).

9. Question: What is the purpose of the namespace keyword in PHP, and how is it used?

   • Answer: The namespace keyword is used to declare a namespace in PHP. It helps in organizing code and avoiding naming conflicts. It is often used at the beginning of a PHP file, and classes within that file are then part of that namespace.

10. Question: Explain the use of the array_map function in PHP.

    • Answer: array_map applies a callback function to each element of an array and returns a new array with the results. It is useful for performing operations on each element of an array without using a loop.

11. Question: What is the significance of PSR standards in PHP, and can you name a few PSR standards?

    • Answer: PSR (PHP Standard Recommendation) standards are a set of coding standards and recommendations agreed upon by the PHP community. Examples include PSR-1 (Basic Coding Standard), PSR-2 (Coding Style Guide), and PSR-4 (Autoloading Standard).

12. Question: How does PHP handle sessions, and what is session fixation?

    • Answer: PHP uses sessions to store user data on the server. Session fixation is a security vulnerability where an attacker sets a user’s session ID to a known value, gaining unauthorized access. Preventive measures include regenerating session IDs and using secure session management practices.

13. Question: What is the purpose of the __construct method in PHP classes?

    • Answer: The __construct method is a constructor in PHP classes. It is automatically called when an object is created and is used to initialize object properties or perform other setup tasks.

14. Question: Explain the use of the final keyword in PHP.

    • Answer: The final keyword is used to prevent a class or method from being extended or overridden by other classes. When applied to a class, it signifies that the class cannot be subclassed.

15. Question: What is the significance of the spl_autoload_register function in PHP?

    • Answer: spl_autoload_register is used to register a custom autoloader function. It allows you to define how classes are loaded, providing flexibility in autoloading mechanisms.

16. Question: How can you handle file uploads in PHP?

    • Answer: File uploads in PHP are handled using the $_FILES superglobal. You need to set the form’s enctype attribute to “multipart/form-data” and use the move_uploaded_file function to move the uploaded file to the desired location.

17. Question: Explain the use of the yield keyword in PHP and its relation to generators.

    • Answer: yield is used in the context of generators to pause execution and return an intermediate result. Generators allow you to iterate over a set of data without loading the entire set into memory at once, improving performance.

18. Question: How can you use sessions to store and retrieve data in PHP?

    • Answer: Sessions in PHP can be used to store and retrieve data using the $_SESSION superglobal. Data stored in $_SESSION persists across multiple requests for the same user.

19. Question: Explain the concept of dependency injection in PHP.

    • Answer: Dependency injection is a design pattern where the dependencies of a class are injected from the outside rather than created within the class. It promotes code flexibility, testability, and maintainability.

20. Question: What is the purpose of the mysqli extension in PHP?

    • Answer: The mysqli extension is used for improved MySQL database connectivity in PHP. It supports features like prepared statements and transactions, enhancing security and performance.

21. Question: How can you use AJAX in PHP applications, and what are its advantages?

    • Answer: AJAX (Asynchronous JavaScript and XML) can be used in PHP applications to enable asynchronous communication between the client and server. This improves user experience by allowing parts of a web page to be updated without requiring a full page reload.

22. Question: Explain the use of the header function in PHP.

    • Answer: The header function is used to send raw HTTP headers in PHP. It is commonly used for tasks such as redirecting the browser, setting cookies, or specifying content types.

23. Question: How can you secure sensitive data, such as passwords, in a PHP application?

    • Answer: Sensitive data should be securely hashed using strong hashing algorithms (e.g., bcrypt) before storage. Additionally, the use of secure, encrypted connections (HTTPS) and secure coding practices should be implemented to protect data during transmission and processing.

24. Question: Explain the concept of CORS (Cross-Origin Resource Sharing) and how it affects PHP applications.

    • Answer: CORS is a security feature implemented by web browsers to control access to resources on a different domain. PHP applications can be affected by CORS restrictions when making cross-origin requests. Proper configuration and handling of CORS headers are necessary to enable or restrict cross-origin resource sharing.

25. Question: How would you optimize the performance of a PHP application?

    • Answer: Performance optimization in PHP can involve various strategies, including code profiling, optimizing database queries, implementing caching mechanisms (e.g., opcode caching), leveraging Content Delivery Networks (CDNs), and using efficient algorithms and data structures. Regular monitoring and analysis are essential for identifying and addressing performance bottlenecks.