The Yii framework is an open-source PHP framework for rapidly-developing, modern Web applications. It is built around the Model-View-Controller composite pattern. Yii provides secure and professional features to create robust projects rapidly.
The Yii framework has a component-based architecture and a full solid caching support. Therefore, it is suitable for building all kinds of Web applications: forums, portals, content managements systems, RESTful services, e-commerce websites, and so forth.
Yii is a pure OOP (Object-Oriented Programming) framework. Hence, it requires a basic knowledge of OOP. The Yii framework also uses the latest features of PHP, like traits and namespaces. The major requirements for Yii2 are PHP 5.4+ and a web server.