I suddenly remembered what assertions are and how they could make my code more readable, while making it shorter. I took a quick look at PHP's assert function, but decided that I don't like it. [...] What I ended up doing was basically to create a class called Assert, and abuse it as a name-space for a whole bunch of useful assertion functions.
He includes two examples of how this new class would look, checking to see if a value is empty and to see if a task ID exists in a given value. The code for the assertion class is also included and has methods for checking things like "not empty", "equals to", "is not numeric" and "is an object". And, no, it's not CakePHP specific, so you could take it an use it anywhere.