title: set the username and id according to facebook's username and id
body: <p>I ve been developing a facebook application on Yii and after the authentication i want to set the username and id according to the facebook username and id. As i am new to Yii I dont't have much idea about how to do it. Though when i tried to set the user id in my UserIdentity class, it gave an error saying that</p>
  
  <pre><code>Property "UserIdentity.id" is read only.
  </code></pre>
  
  <p>is there any other way to do it?</p>