What’s Yii? My Introduction to the Yii Framework at Tuts+ is a great entry point to learn about the framework:
Writing “Hello World” in PHP is quite easy but building an actual web application becomes complicated quickly. As soon as you want to manage security, write DRY code, or leverage MVC design techniques, PHP seems lacking. In the past I’ve worked with Ruby on Rails but found that there’s still a lot that’s hard with it – especially when it comes to hosting and deployment in an economic and flexible manner.
This is where PHP frameworks come in.
There are a number of good PHP frameworks, Symfony, Cake, Zend, CodeIgniter,Laravel and my favorite, Yii. Yii is a free, open-source framework for PHP5 that promotes clean, DRY design, and supports rapid development. I’ve found that Yii offers the breadth of everything I expect from a framework in a high performance package with few of the limitations other PHP frameworks inflict.