Top PHP Interview Questions and Answers

Here are top PHP interview questions,

1. What is PHP?

PHP is a popular server-side scripting language designed for web development. It is included within HTML code and executed on the server to generate dynamic web pages.

 

2. What are the differences between PHP 5 and PHP 7?

PHP 7 introduced significant performance improvements over PHP 5, including a new Zend Engine, reduced memory consumption, and improved error handling. PHP 7 also introduced new features such as scalar type declarations and return type declarations.

 

3. What is the difference between "echo" and "print" in PHP?

Both "echo" and "print" are used to output text, but "echo" is slightly faster and can output multiple values separated by commas, while "print" can only output a single value and returns 1.

 

4. What is the difference between single quotes ('') and double quotes ("") in PHP?

Single quotes ('') treat everything within them as a literal string, while double quotes ("") allow for variable interpolation and escape sequences. Double quotes are more flexible but slightly slower than single quotes.

 

5. What are PHP magic methods?

PHP magic methods are predefined methods that start with "__" (double underscore). They provide functionality to handle certain class operations, such as constructors, destructors, method overloading, property overloading, etc.

 

6. What is the difference between "==" and "===" operators in PHP?

The "==" operator checks for equality after converting the operands to a common type, while the "===" operator checks for strict equality, including the type of the operands.

 

7. How can you prevent SQL injection in PHP?

To prevent SQL injection, you should use prepared statements or parameterized queries with placeholders to separate SQL code from user input. This ensures that user input is treated as data and not executable code.

 

8. What is the difference between "include" and "require" in PHP?

Both "include" and "require" are used to include external files, but "require" generates a fatal error if the file cannot be found or included, while "include" generates a warning and continues script execution.

 

9. What is the difference between GET and POST methods in form submission?

GET method appends form data to the URL and has limitations on the amount of data that can be sent, while POST method sends form data in the body of the HTTP request and is more secure for sensitive information.

 

10. What is the use of the "session_start()" function in PHP?

The "session_start()" function initializes a new or resumes an existing session. It allows you to store and retrieve session data across multiple pages or requests.

 

11. How can you prevent cross-site scripting (XSS) attacks in PHP?

To prevent XSS attacks, you should sanitize user input by using functions such as "htmlspecialchars()" or "strip_tags()" to escape or remove any potentially malicious code before displaying it on a web page.

 

12. What are PHP namespaces?

Namespaces in PHP allow you to organize classes, functions, and constants into a hierarchical structure to avoid naming conflicts. They provide a way to encapsulate and group related code.

 

13. How can you handle file uploads in PHP?

File uploads in PHP can be handled using the $_FILES superglobal array. You can specify an HTML form with the enctype attribute set to "multipart/form-data" and use the move_uploaded_file() function to move the uploaded file to a desired location.

 

14. What is the difference between cookies and sessions in PHP?

Cookies are small files stored on the client-side, while sessions are stored on the server. Cookies can persist across different visits, while sessions are temporary and tied to a specific user session.

 

15. What is the difference between "public", "private", and "protected" visibility in PHP?

"public" members can be accessed from anywhere, "private" members can only be accessed within the defining class, and "protected" members can be accessed within the defining class and its subclasses.

 

16. How can you handle errors and exceptions in PHP?

PHP provides error handling mechanisms such as error reporting levels, custom error handlers using set_error_handler(), and exception handling using try-catch blocks and the "throw" keyword.

 

17. How can you connect to a MySQL database using PHP?

You can connect to a MySQL database using the mysqli or PDO extension in PHP. Both extensions provide functions and methods to establish a connection, execute queries, and retrieve results.

 

18. What is the difference between "array()" and "[]", and when should you use each?

"array()" and "[]" are both used to create arrays in PHP. "[]" is a shorthand syntax introduced in PHP 5.4 and is recommended for new code. However, "array()" is still supported for compatibility with older versions of PHP.

 

19. What is the use of the "foreach" loop in PHP?

The "foreach" loop is used to iterate over arrays and objects in PHP. It automatically assigns the current element's value to a variable for each iteration, making it easy to traverse and process array elements.

 

20. How can you handle file downloads in PHP?

File downloads in PHP can be handled by sending appropriate headers using the header() function. You can set the Content-Disposition header to specify the filename and use readfile() or fopen() functions to output the file contents.

Above are few top PHP interview questions. Remember to prepare and expand on these answers.

Good luck with your interview!  👍