Yii is a high-performance PHP framework best for developing Web 2.0 applications.
Yii comes with rich features: MVC, DAO/ActiveRecord, I18N/L10N, caching, authentication and role-based access control, scaffolding, testing, etc. It can reduce your development time significantly.
Yii only loads the features that you need. It has powerful caching support. It is explicitly designed to work efficiently with AJAX.
Security comes as standard with Yii. It includes input validation, output filtering, SQL injection and Cross-site scripting prevention.
Yii helps you develop clean and reusable code. It follows the MVC pattern, ensuring a clear separation of logic and presentation.