# Yii2 — Fast Secure Professional PHP Framework

> Yii2 is a high-performance component-based PHP framework for developing modern web applications with built-in security, caching, and RESTful API support.

## Install

Save in your project root:

# Yii2 — Fast Secure Professional PHP Framework

## Quick Use
```bash
composer create-project --prefer-dist yiisoft/yii2-app-basic myapp
cd myapp
php yii serve
```

## Introduction
Yii2 is a full-stack PHP framework optimized for performance through lazy loading and code generation. It provides a structured MVC architecture with strong conventions while remaining flexible enough for any web project.

## What Yii2 Does
- Provides a full MVC architecture with code generation via Gii
- Includes built-in ActiveRecord ORM for database access
- Offers robust authentication, authorization, and RBAC
- Supports RESTful API development with serialization and rate limiting
- Includes asset management, caching, and i18n out of the box

## Architecture Overview
Yii2 uses a component-based architecture where the application object orchestrates requests through a pipeline of modules, controllers, and actions. It implements lazy loading extensively, only instantiating components when first accessed. The framework uses a service locator pattern and supports dependency injection through its DI container.

## Self-Hosting & Configuration
- Install via Composer with basic or advanced project templates
- Configure database connections in `config/db.php`
- Run migrations with `php yii migrate`
- Use Gii code generator at `/gii` during development
- Deploy behind Nginx or Apache with standard PHP-FPM

## Key Features
- Gii code generator for models, controllers, and CRUD scaffolding
- Two-tier caching with dependency invalidation support
- Built-in RBAC with database or file-based storage
- Debug toolbar and profiler for development
- Extensible widget system for reusable UI components

## Comparison with Similar Tools
- **Laravel** — more opinionated with Eloquent ORM; Yii2 offers comparable features with different conventions
- **Symfony** — component-focused; Yii2 provides a more integrated full-stack experience
- **CakePHP** — convention-over-configuration; Yii2 emphasizes code generation and performance
- **CodeIgniter** — lighter weight; Yii2 includes more built-in features like RBAC and asset pipeline
- **Laminas (Zend)** — enterprise-oriented; Yii2 balances enterprise features with developer productivity

## FAQ
**Q: Is Yii2 still actively maintained?**
A: Yes. Yii2 receives security patches and bug fixes. Yii3 is also in development as the next major version.

**Q: How does Yii2 handle database migrations?**
A: Yii2 includes a migration tool accessed via `php yii migrate` that supports versioned schema changes.

**Q: Can Yii2 build APIs?**
A: Yes. Yii2 has dedicated REST controller classes with built-in serialization, pagination, rate limiting, and content negotiation.

**Q: What PHP version does Yii2 require?**
A: Yii2 requires PHP 7.3 or higher, with PHP 8.x fully supported.

## Sources
- https://github.com/yiisoft/yii2
- https://www.yiiframework.com/doc/guide/2.0/en

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Author: AI Open Source