Yii is am open source generic web programming framework that suitable
for developing large-scale applications such as portals, forums,
content management systems (CMS), e-commerce projects etc.
Like most PHP frameworks, Yii implements the MVC (Model-View-Controller) architectural pattern and promotes code organization based on that pattern.
Yii takes the philosophy that code should be written in a simple yet elegant way. Yii will never try to over-design things mainly for the purpose of strictly following some design pattern.
Yii is a full-stack framework providing many proven and ready-to-use features: query builders and ActiveRecord for both relational and NoSQL databases; RESTful API development support; multi-tier caching support; and more.
Yii is extremely extensible. You can customize or replace nearly every piece of the core's code. You can also take advantage of Yii's solid extension architecture to use or develop redistributable extensions.
High performance is always a primary goal of Yii.