If you are testing your app and use urlManager in your config, sometimes you will find a problem: you want to test your site independing from urlManager settings. in that way you need to extend your WebTestCase class by this method:
In many cases developers of one project use their own local environments for coding. There may be a common test platform and, of course, production. All these environments usually have different DB credentials and directory structures (first of all, path to YII framework directory). Another feature is debugging. It's convenient to turn it on for local environments, eventually - on the test server and never (generally speaking) - on the production.
Many applications wish to obtain parts of the URL for the current page (the hostname, the query string, etc.), and the CHttpRequest class wraps various $_SERVER variables to break down the URL into its constituent parts.