# CodeIgniter 4 — Proven Lightweight PHP Framework

> CodeIgniter 4 is a lightweight full-stack PHP framework known for its small footprint, fast performance, and straightforward documentation, making it one of the easiest PHP frameworks to learn.

## Install

Save in your project root:

# CodeIgniter 4 — Proven Lightweight PHP Framework

## Quick Use
```bash
composer create-project codeigniter4/appstarter myapp
cd myapp && php spark serve
```

## Introduction
CodeIgniter 4 is a complete rewrite of the original CodeIgniter framework, modernized with PHP 8 support, namespaces, PSR compliance, and a built-in CLI tool called Spark. It maintains the framework's tradition of a small footprint and clear documentation while adding features expected in a modern PHP framework like an ORM, migrations, and a testing library.

## What CodeIgniter 4 Does
- Provides MVC architecture with controllers, models, and view templates
- Includes a query builder and simple ORM for database operations
- Runs a built-in development server via `php spark serve`
- Supports database migrations, seeding, and schema management
- Offers a CLI tool (Spark) for code generation and common tasks

## Architecture Overview
CodeIgniter 4 follows the Model-View-Controller pattern with a front controller that routes all requests through `public/index.php`. The routing system supports both defined routes and automatic controller method discovery. The framework loads only the components needed for each request, keeping memory usage low. Services are accessed through a service locator pattern, and configuration is handled via PHP classes rather than arrays or YAML files.

## Self-Hosting & Configuration
- Install with Composer: `composer create-project codeigniter4/appstarter`
- Configure the database in `app/Config/Database.php` with connection details
- Set the base URL and environment in `.env` (development, testing, production)
- Run migrations with `php spark migrate` to apply database schema changes
- Deploy to Apache or Nginx with a standard PHP-FPM configuration

## Key Features
- Extremely small framework core with fast request processing
- Built-in RESTful resource routing for API development
- Shield authentication library for login, registration, and 2FA
- Honeypot and CSRF protection included by default
- Comprehensive testing library with mock HTTP requests and database testing

## Comparison with Similar Tools
- **Laravel** — more features and larger ecosystem, heavier runtime footprint
- **Symfony** — enterprise-grade component library, steeper learning curve
- **Slim** — micro framework for APIs only, no ORM or view layer
- **CakePHP** — convention-over-configuration approach, similar maturity, more opinionated

## FAQ
**Q: How does CodeIgniter 4 compare to Laravel in performance?**
A: CodeIgniter 4 generally has lower memory usage and faster request times due to its smaller core. Laravel offers more built-in features at the cost of that overhead.

**Q: Does CodeIgniter 4 support PHP 8?**
A: Yes. CodeIgniter 4 requires PHP 8.1 or higher and takes advantage of modern PHP features like enums, fibers, and named arguments.

**Q: Is CodeIgniter 4 good for REST APIs?**
A: Yes. It includes a ResourceController base class and content negotiation for building RESTful services without additional packages.

**Q: Can I use Eloquent ORM with CodeIgniter 4?**
A: Technically possible via Composer, but the framework's built-in Model and Query Builder are designed to work together. Mixing ORMs adds complexity.

## Sources
- https://github.com/codeigniter4/CodeIgniter4
- https://codeigniter.com

---
Source: https://tokrepo.com/en/workflows/asset-40ba68dd
Author: AI Open Source