Yii Knowledge Base

Quick reference for Yii3 framework patterns and PHP implementation guidelines. Yii3 is a complete rewrite — modular, PSR-compliant, and designed for modern PHP 8.4+ applications with clean architecture support.

Core Principles

PSR Compliance

Yii3 implements PSR-3 (log), PSR-4 (autoload), PSR-7/PSR-17 (HTTP messages/factories via yiisoft/http-message), PSR-11 (DI via yiisoft/di), PSR-12 (coding style), PSR-15 (middleware via yiisoft/middleware-dispatcher).

Middleware Pipeline

Request → [Router] → [Auth] → [CORS] → [Action] → Response
              ↓                            ↓
         yiisoft/router            Application Logic

Rule: All HTTP handling flows through the PSR-15 middleware pipeline. No global state.