Is it fast? ... Is it secure? ... Is it professional? ... Is it right for my next project? ... Yes, it is! Yii is a high-performance component-based PHP framework best for Web 2.0 development. Yii helps Web developers build complex applications and deliver them on-time. Yii is a free, open-source Web application development framework written in PHP5 that promotes clean, DRY design and encourages rapid development. It works to streamline your application development and helps to ensure an extremely efficient, extensible, and maintainable end product.