You should use a Component for that. Components are objects that can be used across any controller (as long as you include it in the controller's $components
property, or in that of the AppController).
For example, if you have any experience with Auth
in Cake, that's a Component, and its methods can be called from any controller.
More info about components here: http://book.cakephp.org/2.0/en/controllers/components.html
If you need more help, feel free to try and write a component yourself and come back with any problems you might have.