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.
Large applications are often divided into front-end and back-end (or even more ends) depending on the target user groups. The front-end should be used by common users, while the back-end mainly the administrators or staff members. The two ends usually have dramatically different appearance, even though they may share a lot of code underneath. In this tutorial, we describe a way of organizing directories of the code for both ends.