PHP Interview Questions and Answers 2025

PHP is a server-side scripting language designed for web development.

Use the '$' symbol followed by the variable name, e.g., \$variableName.

The 'echo' statement is used to output data to the screen.

Use '//' for single-line comments and '/* */' for multi-line comments.

Both include files, but 'require' causes a fatal error if the file is not found, while 'include' only gives a warning.

Use the 'function' keyword followed by the function name and parentheses, e.g., function myFunction() {}

The 'isset()' function checks if a variable is set and is not NULL.

Use the 'mysqli_connect()' function with parameters for host, username, password, and database name.

'==' checks for value equality, while '===' checks for both value and type equality.

Use '<?php' to start a PHP block.

The 'array()' function is used to create an array.

Use 'try-catch' blocks or error handling functions like 'set_error_handler()'.

The 'strlen()' function returns the length of a string.

Use the 'file_exists()' function.

The 'session_start()' function initializes a session or resumes the current one.

Namespaces are used to avoid name conflicts in large applications by encapsulating classes, interfaces, functions, and constants.

An abstract class can have both abstract and concrete methods, while an interface can only have abstract methods.

Use the 'extends' keyword to inherit properties and methods from a parent class.

The 'final' keyword prevents a class from being extended or a method from being overridden.

Use 'try-catch' blocks to catch exceptions and handle them gracefully.

Traits are used to include reusable methods in multiple classes without using inheritance.

'Public' allows access from anywhere, 'protected' allows access within the class and its subclasses, and 'private' restricts access to the class itself.

The 'static' keyword is used to declare properties or methods that belong to the class rather than an instance.

The 'autoload' function automatically loads classes or interfaces when they are needed.

Use the 'define()' function or the 'const' keyword to declare a constant.

Both include files only once, but 'require_once' causes a fatal error if the file is not found, while 'include_once' only gives a warning.

The 'PDO' extension provides a consistent interface for accessing databases and supports prepared statements for security.

Magic methods like '__construct', '__destruct', '__get', and '__set' provide special functionality when interacting with objects.

Use the 'serialize()' function to convert data into a storable format and 'unserialize()' to convert it back.

A closure is an anonymous function that can capture variables from its surrounding scope.

Dependency injection is a design pattern where an object receives its dependencies from an external source rather than creating them itself.

The Reflection API allows inspection of classes, methods, properties, and more at runtime.

To implement Singleton, create a private constructor, a static method to get the instance, and a static property to hold the instance.

The 'yield' keyword is used to create a generator, which allows iteration over data without storing it in memory.

Use libraries like ReactPHP or Swoole for asynchronous programming in PHP.

Composer is a dependency manager for PHP that helps manage libraries and packages in a project.

Use frameworks like Laravel or Slim to create RESTful APIs, adhering to HTTP methods and status codes.

Sessions store data on the server, while cookies store data on the client-side in the browser.

Use prepared statements with parameterized queries, such as those provided by PDO or MySQLi.

OPcache improves performance by caching precompiled script bytecode in memory.

Middleware is implemented as a layer that processes requests and responses, commonly used in frameworks like Laravel.

Soft delete marks a record as deleted without removing it from the database, while hard delete permanently removes it.

The SPL provides data structures, iterators, and interfaces to solve common problems in PHP.

The Phar extension allows packaging PHP applications into a single file for distribution.

Use 'set_error_handler()' to define a custom error handling function.

Lazy loading fetches related data only when accessed, while eager loading fetches it upfront to reduce queries.

The 'namespace' keyword organizes code into logical groups and avoids name conflicts.

The Garbage Collector manages memory by cleaning up unused objects and circular references.

Use libraries like Ratchet or Swoole to implement WebSocket servers for real-time communication.

CLI is used for running PHP scripts from the command line, while CGI is used for executing scripts via a web server.