Yii is a high-performance component-based PHP framework for developing large-scale Web applications. Yii enables maximum reusability in Web programming and can significantly accelerate the development process. The name Yii (pronounced as [i:]) stands for easy, efficient and extensible.
Yii is easy to learn and use. You only need to know PHP and object-oriented programming. You are not forced to learn a new configuration or templating language.
Yii is extremely fast. Its overhead to applications written on top of it is negligible. As a matter of fact, it is one of the most efficient PHP frameworks around.
Yii is highly reusable and extensible. Yii is purely object-oriented. Everything in Yii is a self-contained component which can be configured, reused or extended easily.