title: In an Observer method, how do you tell Magento to not process code after the dispatched event
body: <p>I have some code in the checkout where I set a key in the session if that key is set to false anywhere in the checkout I need to send them back to the billing page. I have the code for it, but I also can't have any of the code that is typically ran after the observer because it will call a third party service and come back as wrong because of this key that is missing in the session</p>
  
  <p>Here is my code, I  have everything I want but i need the response to happen immediatly and for nothing after the dispatched event line to be fired only the response sent back to the browser.</p>
  
  <pre><code>public function checkForOrdKey(Varien_Event_Observer $observer)
      {
          $controllerAction = $observer-&gt;getControllerAction();
          $request = $controllerAction-&gt;getRequest();
          $controllerName = $request-&gt;getControllerName();
          $stepData = $this-&gt;_getCheckoutSession()-&gt;getStepData();
          $ordKeyRemoved = $this-&gt;_getCheckoutSession()-&gt;getOrdKeyRemoved();
          // if it is the checkout onepage controller or inventory controller don't do anything
          if (isset($controllerName) &amp;&amp; $controllerName === "onepage" &amp;&amp; $stepData['shipping']['complete'] &amp;&amp; $ordKeyRemoved) {
              $this-&gt;_getCheckoutSession()-&gt;setStepData('shipping', 'complete', false);
              $result['goto_section'] = 'billing';
              Mage::app()-&gt;getResponse()-&gt;setBody(Mage::helper('core')-&gt;jsonEncode($result));
              $this-&gt;_getCheckoutSession()-&gt;setOrdKeyRemoved(false);
  
          }
      }
  </code></pre>