Calling a controller within a controller (no URL redirect)

[eluser]Tjunction[/eluser]
Is this possible at all? Not in the redirect the user to a different URL sense, but to call a method on a different controller, receive the response, use this in the same method and then echo the result out to the user.

I have require_once'd the controller in question, then added the following;

Code:

$runsheet_controller = new Runsheet_controller();

But this errors out with the following -

A PHP Error was encountered
Severity: Notice
Message: Undefined property: Runsheet_controller::$controller_session
Filename: job/Runsheet_controller.php
Line Number: 104

I've had a bit of a look over the load function of CI etc, but as far as I can see it can't load a controller... any help would be much appreciated