title: Yii::app()->user->id; is returning username instead of id number
body: <p>I have a very strange problem in that on one machine <code>Yii::app()-&gt;user-&gt;id;</code> returns the username, but on another machine running identical code I'm getting the id number as expected. 
  How could <code>Yii::app()-&gt;user-&gt;id</code> be getting the username? What have I missed? </p>