Throwing exceptions when appropriate is a much cleaner way to handle errors in your PHP applications than the usual return false; and the inevitable if statement to check whether your method call worked. Not only does it make your code cleaner, you actually get some information about the error.

In a CakePHP MVC structure it’s fun to throw Exceptions from your models, but including a try/catch in every single controller method starts to get unwieldy. Instead you can create an exception handler in your AppController, something like this:

    public function beforeFilter()
    {
        set_exception_handler(array($this, 'handleException'));
        parent::beforeFilter();
    }

    public function handleException(Exception $exception)
    {
        try
        {
            throw $exception;
        }
        catch (ResourceNotFoundException $ex)
        {
            $this->cakeError('error404', array('message' => $ex->getMessage()));
        }
        catch (Exception $ex)
        {
            $this->cakeError('error500', array('message' => $ex->getMessage()));
        }
    }

Notice that we can rethrow the exception in the handler to avoid using an if or switch construct. Now in our controller method we can write code like this:

         $bagpuss = $this->Bagpuss->read(null, $id);
         if (!$bagpuss)
         {
             throw new ResourceNotFoundException('Could not find bagpuss');
         }

We could even go as far as to override read() in AppModel to throw a ResourceNotFoundException to simplify our controllers further, though I worry this will (a) break existing tools (change of contract), and (b) create too much dependency between model and controller.

Comments or suggestions welcome.