title: Watson Conversation: Check and act on existence of context variable?
body: <p>I am using <a href="https://console.bluemix.net/docs/services/conversation/index.html#about" rel="nofollow noreferrer">IBM Watson Conversation service</a> and slots within a dialog node. In the response I want to return the value of a context variable that is gathered with a slot. However, I cannot be sure that the variable exists because the user could have cancelled the input process and because the variable is optional. How can I check the existence and act depending on that check?</p>
  
  <p>Using this</p>
  
  <pre><code>&lt;? $myVariable ?&gt;
  </code></pre>
  
  <p>gives an error when the variable is not present.</p>