What’s “normal” PHP for you? Yii deals with classes and methods. renderPartial() is CController’s method and it calls include() function, but it can’t see variables of other renderPartial() methods, because all of them are local.
The actual implementatio of the render require that all variable are passed view by view.
You can also access to the controller with $this, so if you want to share some variable withoout passing all time, you can use a property of the controller.
in controller:
public $var;
in all views:
$this-var
This is how is implemented breadcrumbs and menu, there are some property in the master class Controller that you can find in /compoment