In the sixth part of his series on creating a custom framework on top of the Symfony2 components, Fabien Potencier looks at how to improve the previous examples by swapping out the more procedural controllers with actual classes.
The move is pretty straightforward and makes a lot of sense as soon as you create more pages but you might have noticed a non-desirable side-effect... The LeapYearController class is always instantiated, even if the requested URL does not match the leap_year route. This is bad for one main reason: performance wise, all controllers for all routes must now be instantiated for every request. It would be better if controllers were lazy-loaded so that only the controller associated with the matched route is instantiated.
To help solve the issue, he uses the HttpKernel component and its "controller resolver" to figure out how to call the controller and pass it the correct parameters, but only when needed. A resolver object is created and that is used to instantiate the controller object. Sample "action" calls are included to fill out the basic controller (his "leap year" example) and the full resulting code is included both for the framework and the new object oriented controller.