title: Calling unexisting controller, how to generate exception?
body: <p>I'm writing my own little MVC and I got a question... I'm passing <code>$_SERVER['REQUEST_URI']</code> to the <code>Router</code> class which returns me controller, it's action and array of GET parameters.
  (For example Router said that I should call <code>App_Controller-&gt;index()</code>).</p>
  
  <p>So, I should create instance of <code>App_Controller</code> and call <code>index()</code> method. So, I'm doing something like <code>$controller = new $controller_name</code> etc. But what if controller is not found by <code>spl_autoload_register()</code> (I'm using autoload). </p>
  
  <p>How can I generate Exception about the fact that controller is not found? Or maybe I'm doing something wrong?</p>
  
  <p>Thank you.</p>