Dear ZF-guru's,

The past few days I've tried to sort out the error handling in ZF, I quite like the idea of throwing custom Exceptions, like so:

Handling errors in Zend Framework | CodeUtopia - The blog of Jani Hartikainen

However, if I want it to work like it says of there, where do I put which exception class?

For example I have a userController that I want to be able to throw a userNotFoundException in case (as the name suggests) the user is not found.

Where would I put the userNotFoundException class? And would I let it extend the Zend_Exception class?