Say you’re doing some simple display logic for a controller view:

function view($id=null)
{
    if ($id) {
           $this->set($data,$this->Model->findById($id));
    } else {
           return false;
    }

}

In a situation like this, you always want to handle the (inevitable) situation when someone requests an invalid ID number, at which point no data would be returned in the $data variable.

Luckily, there’s a handy little function called cakeError, which lets you call a variety of Cake errors. Most of the time, you’ll want a 404 error, but it also lets you call any Cake-standard errors (you can see the full list here).

Regardless, if you want Cake to display a “404 Not Found” error message if the ID isn’t found or returns no data, do something like the following:

function view($id=null)
{
    if ($id) {
           $data = $this->Model->findById($id);
           if (!$data) {
                 $this->cakeError('error404',array(array('url'=>'/')));
           } else {
                 $this->set('data',$data);
           }

    } else {
           return false;
    }

}

That will throw up Cake’s generic 404 error page and stop further script execution for ya. If you want to have a custom 404 page, add a file named “error404.ctp” to your /app/views/error/ directory.