I was quickly told by the friendly people in #php_bnl on irc.freenode.net that I needed to use Decorators for that, so I went diving into the documentation. Reading the official documentation, I couldn't really get into how exactly the decorators worked and what I could do with them.

It was this article on the Zend Developer Zone that helped him the most, though. He explains his solution, defining the Decorator with a setDecorator method call, and includes the one-liner that made it work.