Edit:
Classes inside protected/controllers are not autoloaded, therefore you'll have to import the parent class file before extending from it:
In AnotherController.php:
Yii::import('application.controllers.SomeController');
public class AnotherController extends SomeController {
// ...
}
Incase you need to access the base class from url also, you can use the above method. Otherwise you can put your base class inside protected/components as you have already figured out.
Yii autoloading works only when you have the same name for the file as the class that the file contains. Meaning class SomeController
should be within SomeController.php file.
Make those changes and it should work.
A helpful wiki: Understanding Autoloading Helper Classes and Helper functions.
Class files should be named after the public class they contain.