You have a multilingual application, and you want the URL of a page to be different for different languages, to account for SEO. The URL for the contact page for example should look like http://something.com/en/contact in english, and http://something.com/de/contact in german. This tutorial describes how to make it happen.
Note that currently selected language is always a part of the URL, and thus available to the application through $_GET. You don't have to use sessions variables to keep track of the language if you don't want to.
The Definitive Guide introduces the fundamentals of managing URLs in a Yii application. In this tutorial, we introduce a practical technique that can quickly turn your application into using search-engine-friendly URLs.
I recently created a project called Yii-App on GitHub to kickstart my development of smaller Yii applications. The main goal of the project is to provide a ready-to-use application template that includes my bootstrap extension and many other useful extensions. After reading this article you will be able to use this project as a starting point for all of your Yii projects.