By default, the expression Yii::app()->user returns a CWebUser application component which represents the information that are closely related with the current user. Some information can be persistent throughout the current user session. For example, CWebUser already comes with a name property that stores the username of the current user.
The customary configuration of a Yii application includes just a single database section in the protected/config/main.php file, but it's easy to extend this to support more than one, tying each Model to one of the databases.
Many Yii users ask how to create helper classes and functions, and though there are numerous approaches spread out among the forum and wiki articles, this Tutorial tries to bring it all together in one place.