Yii is an open source, object-oriented, component-based MVC PHP web application framework. Yii is a generic Web programming framework. Yii implements the MVC (Model-View-Controller) architectural pattern and promotes code organization based on that pattern. Yii is a full-stack framework providing many proven and ready-to-use features. Yii is extremely extensible. Developer can customize or replace nearly every piece of the core’s code.