YII, which stands for Yes It Is, is a free open-source Web Application Development Framework that comes from the house of PHP5. Known for its optimized and impressive performance, it gains a significant edge over other PHP Frameworks. It is also touted as the fastest PHP framework, the very reason why it is used for large scale Web 2.0 projects. This powerful and high-performance framework is especially useful for the development of high traffic platforms such as portals, social networking sites, forums, popular blogs, etc. The framework is packed with a number of features such as DAO, MVC, scaffolding, skinning, authentication, caching and testing among others. These features when coupled with AJAX-based widgets make YII a very useful web development framework.