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.
You may have scenarios, where you want to store a specific array configuration to the database. A classic example could be saving Yii widget configuration to the database and then retrieving it at runtime, with dynamic parameters set. This wiki discusses one of the approaches to do this. Let's consider you have something like the NavBar configuration below to store in the db:
It is difficult to perform user dependent theming through a general configuration in 'main.php'.
This article proposes a method to do so through a Factory that dynamically generates classes to allow delayed resolution of actual user values.
This means that you can refer to values that are stored in the database through the CActiveRecord before Yii is actually loaded.
The values will be fetched from the database when actually used for the first time, which is after Yii is loaded.
Actually, you can use pretty much any method that relies on Yii with this method.
If you develop your Yii project on both Windows and Mac, there can be a problem setting up the configuration unless the configurations for both system are identical.
On my machines I have the following configurations: