Yii is a high-performance PHP framework which has powerful caching support and is explicitly designed to work efficiently with AJAX. Security is important, and that's why Yii includes input validation, output filtering, SQL injection and Cross-site scripting prevention. As Yii follows the MVC pattern, it helps you develop clean and reusable code, ensuring a clear separation of logic and presentation. You can model database data in terms of objects and avoid the complexity and tedious nature of writing repetitive SQL statements. Collecting form input is both safe and easy, as Yii comes with a set of validators as well as numerous helper methods and widgets. There is support for writing and running unit tests and functionality tests, along with efficient error handling, and log messages can be categorized, filtered and routed to different destinations. As Yii is designed to work well with third-party code, you can integrate other frameworks data into your Yii powered application.