PHP Interview Questions

Question 1

What is PHP and what is it used for?

Accepted Answer

PHP is a server-side scripting language primarily used for web development, powering WordPress, Laravel, and 77% of websites. PHP: Hypertext Preprocessor. Embedded in HTML with <?php ?>. Powers WordPress (43% of web), Facebook (Hack), Wikipedia. Strengths: easy to learn, huge ecosystem, excellent hosting support. Modern PHP (8.x): typed properties, match expressions, enums, fibers, readonly classes.

Question 2

What are PHP data types?

Accepted Answer

PHP has scalar types (string, int, float, bool), compound types (array, object), and special types (null, resource). PHP is dynamically typed but supports type declarations (PHP 7+). Type juggling: automatic conversion. Strict mode: declare(strict_types=1). Union types (PHP 8): int|string. Intersection types: A&B. Arrays are versatile: indexed, associative, multidimensional. Type coercion can cause subtle bugs.

Question 3

What is Laravel and its key features?

Accepted Answer

Laravel is a PHP framework with Eloquent ORM, Blade templates, Artisan CLI, middleware, routing, and built-in auth. Key features: (1) Eloquent ORM: ActiveRecord pattern. (2) Blade: template engine. (3) Artisan: CLI for scaffolding. (4) Middleware: request pipeline. (5) Laravel Sanctum/Passport: API auth. (6) Queues: background jobs. (7) Laravel Sail: Docker dev environment. (8) Livewire: full-stack reactive components.

Question 4

How does PHP handle sessions and cookies?

Accepted Answer

Sessions store data server-side (identified by session ID cookie); cookies store small data client-side with expiry. session_start() begins session. $_SESSION superglobal for read/write. Session ID in cookie (PHPSESSID). Cookies: setcookie(name, value, expire). $_COOKIE to read. Sessions: more secure (data server-side), larger storage. Cookies: persist across visits, limited to 4KB. Use sessions for auth state, cookies for preferences.

Question 5

What is Composer?

Accepted Answer

Composer is PHP's dependency manager, using composer.json for packages and autoloading via PSR-4. composer require package: installs dependency. composer.lock: locks versions. Autoloading: PSR-4 standard. Packagist.org: default repository. Semantic versioning: ^2.0 (minor updates). Scripts: custom commands. Platform requirements: specify PHP/extension versions. composer update vs install (lock file).

Question 6

What are PHP 8's new features?

Accepted Answer

Named arguments, match expressions, union types, attributes, enums, fibers, readonly properties, and JIT compilation. PHP 8.0: union types, named arguments, match expression, nullsafe operator (?->), attributes (#[Route('/')]). PHP 8.1: enums, fibers, readonly properties, intersection types. PHP 8.2: readonly classes, standalone types (true, false, null). PHP 8.3: typed class constants, json_validate(). JIT compiler improves CPU-bound performance.

Question 7

How do you secure a PHP application?

Accepted Answer

Use prepared statements, input validation, output escaping, CSRF tokens, password hashing, HTTPS, and up-to-date dependencies. Security: (1) SQL injection: PDO prepared statements. (2) XSS: htmlspecialchars() output escaping. (3) CSRF: token-based protection. (4) Passwords: password_hash()/password_verify() with bcrypt. (5) File uploads: validate type/size. (6) Dependencies: composer audit. (7) Headers: Content-Security-Policy, X-Frame-Options. (8) HTTPS everywhere. (9) Session security: regenerate ID on login.

Question 8

How do you optimize a slow Laravel application?

Accepted Answer

Profile with Laravel Debugbar, fix N+1 queries with eager loading, add caching (Redis), optimize routes and config. Steps: (1) Laravel Debugbar: see queries and timing. (2) Eager loading: with() to fix N+1. (3) Redis caching for frequent queries. (4) Route caching: php artisan route:cache. (5) Config caching: php artisan config:cache. (6) Queue heavy operations. (7) Database indexes. (8) OPcache enabled. (9) Pagination for large results.

Question 9

Facebook: Why did Facebook create Hack from PHP?

Accepted Answer

Facebook created Hack to add static typing, async/await, and generics to PHP for better performance and developer productivity. Hack: gradually typed PHP superset. Added: static typing (annotations), async/await (non-blocking I/O), generics, collections (typed alternatives to arrays), XHP (type-safe HTML). Runs on HHVM (HipHop Virtual Machine) with JIT compilation. Facebook processes billions of requests daily. Key lesson: static typing at scale catches bugs earlier and enables better tooling.

Question 10

Free PHP Course - Learn Web Development, MySQL & Laravel Basics

What You'll Learn

Career Opportunities

Course Completion Certificate

Course Modules Overview

Introduction to PHP

Variables, Data Types & Operators

Control Structures and Loops

Functions and Scope

Arrays and Array Functions

Strings and Regular Expressions

Object-Oriented PHP

Database and MySQL Integration

Sessions Cookies and Security

PHP Project: Blog CMS

Laravel Framework & Modern PHP

PHP Career & Enterprise Development

Course Curriculum

Introduction to PHP

Variables, Data Types & Operators

Control Structures and Loops

Functions and Scope

Arrays and Array Functions

Strings and Regular Expressions

Object-Oriented PHP

Database and MySQL Integration

Sessions Cookies and Security

PHP Project: Blog CMS

Laravel Framework & Modern PHP

PHP Career & Enterprise Development

Your Learning Path

Beginner

Intermediate

Advanced

Tools & Technologies

XAMPP

VS Code

phpMyAdmin

Ready to Start Learning?

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