The Yii Book by Larry Ullman
Developing Web Applications Using the Yii PHP Framework.
Yii uses pure Object-Oriented Programming (OOP). Unlike some other frameworks, Yii has always required version 5 of PHP. This is significant,as PHP 5 has a vastly improved and advanced object structure compared with the older PHP 4.
Is it fast?. . . Is it secure?. . . Is it professional?. . . Is it right for my next
project?. . . Yes, it is!