PHP is one of the most popular programming languages for web development. If you’re preparing for a PHP job interview, you need to be well-versed with the essential concepts. In this article, we will cover the top 50 PHP interview questions and answers to help you ace your next interview.
Basic PHP Interview Questions
Q1. What is PHP?
A: PHP stands for Hypertext Preprocessor. It is an open-source, server-side scripting language designed for creating dynamic web pages.
Q2. What are the common uses of PHP?
A: PHP is commonly used for:
- Server-side scripting
- Command-line scripting
- Creating dynamic websites
- Interacting with databases (e.g., MySQL)
- Building RESTful APIs
Q3. How do you declare a variable in PHP?
A: Variables are declared using the $ symbol, e.g., $name = "John";.
Q4. What are PHP data types?
A: PHP supports:
- String
- Integer
- Float (Double)
- Boolean
- Array
- Object
- NULL
- Resource
Q5. What is the difference between echo and print?
A:
-
echo: Outputs data, can take multiple parameters, no return value. -
print: Outputs data, returns 1, works like a function.
Q6. How do you define a constant in PHP?
A: Using the define() function, e.g., define("SITE_NAME", "Shikshatech");.
Q7. What are PHP magic constants?
A: Special constants starting with double underscores, like:
__LINE____FILE____DIR____FUNCTION____CLASS__
Q8. What is the difference between == and ===?
A:
-
==: Compares values only. -
===: Compares values and data types.
Q9. What is a session in PHP?
A: Sessions allow data to be stored across multiple pages. session_start() is used to initiate a session.
Q10. What is a cookie in PHP?
A: Cookies are small files stored on the client’s device. Created using setcookie().
Intermediate PHP Interview Questions
Q11. What is the difference between GET and POST?
A:
-
GET: Sends data via URL, limited length, less secure. -
POST: Sends data via HTTP headers, no limit, more secure.
Q12. What are arrays in PHP?
A: Arrays are collections of data:
-
Indexed Arrays:
$fruits = array("Apple", "Banana", "Mango"); -
Associative Arrays:
$age = array("John" => 30, "Jane" => 25); -
Multidimensional Arrays:
$marks = array("John" => array(90, 85), "Jane" => array(78, 88));
Q13. Explain PHP error types.
A:
- Notice: Non-critical errors (e.g., undefined variables).
- Warning: Recoverable errors (e.g., missing files).
- Fatal Error: Non-recoverable errors (e.g., calling undefined functions).
- Parse Error: Errors in code structure.
Q14. What is isset()?
A: Checks if a variable is set and is not NULL. Returns true if the variable exists and is not NULL.
Q15. What is empty()?
A: Checks if a variable is empty. Returns true if it is NULL, 0, "", false, or an empty array.
Q16. What are PHP filters?
A: Filters are used to validate and sanitize data. Example: filter_var($email, FILTER_VALIDATE_EMAIL);.
Q17. What is PDO in PHP?
A: PHP Data Objects (PDO) is a database access layer that provides a uniform interface for multiple databases.
Q18. How do you connect to a MySQL database using PDO?
A:
$pdo = new PDO("mysql:host=localhost;dbname=testdb", "username", "password");
Q19. What is SQL Injection? How to prevent it?
A: SQL Injection is a technique where attackers inject malicious SQL queries.
Prevention: Use prepared statements and parameterized queries.
Q20. What is a trait in PHP?
A: A trait is a code reuse mechanism used to include methods in a class without inheritance.
Advanced PHP Interview Questions
Q21. What is Object-Oriented Programming (OOP) in PHP?
A: A programming model organized around objects rather than actions. Core concepts include classes, objects, inheritance, polymorphism, encapsulation, and abstraction.
Q22. What are Namespaces in PHP?
A: Namespaces provide a way to group related classes, functions, and constants to avoid naming conflicts.
Q23. Explain the MVC architecture.
A: MVC stands for Model-View-Controller. It separates application logic, presentation, and user interaction.
Q24. What is Composer in PHP?
A: Composer is a dependency manager for PHP, allowing you to manage libraries and packages in your projects.
Q25. What is the difference between include and require?
A:
-
include(): Produces a warning if the file is missing but continues execution. -
require(): Produces a fatal error if the file is missing and stops execution.
Q26. What is json_encode() and json_decode()?
A: Functions to convert data between JSON format and PHP arrays/objects.
Q27. How to handle file uploads in PHP?
A: Using the $_FILES superglobal and moving files via move_uploaded_file().
Q28. Explain PHP's session_destroy() function.
A: Destroys all data registered to a session and deletes the session itself.
Q29. What is OPcache?
A: A built-in caching engine that improves PHP performance by storing precompiled script bytecode in memory.
Q30. How to improve PHP performance?
A:
- Use caching (OPcache, Memcached).
- Optimize database queries.
- Minimize file I/O.
- Use CDN for static resources.
- Code refactoring.
Our Best Top 50 PHP Interview Questions and Answers | Shikshatech
Top 50 PHP Interview Questions and Answers to Ace Your Next Job Interview | PHP Interview Questions
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