Going from the Controller to the View

I am working on creating my own very simple MVC and I am brainstorming ways to go from the controller to the view. Which involves sending variables from a class to just a plain old PHP page.

I am sure that this has been covered before, but I wanted to see what kind of ideas people could come up with.

//this file would be /controller/my_controller.php

class My_Controller{

   function someFunction(){

  $var = 'Hello World';
  //how do we get var to our view file in the document root?
  //cool_view.php

   }

}