title: What does it mean to start a PHP function with an ampersand?
body: <p>I'm using the Facebook library with this code in it:</p>
  
  <pre><code>class FacebookRestClient {
  ...
      public function &amp;users_hasAppPermission($ext_perm, $uid=null) {
          return $this-&gt;call_method('facebook.users.hasAppPermission', 
          array('ext_perm' =&gt; $ext_perm, 'uid' =&gt; $uid));
      }
  ...
  }
  </code></pre>
  
  <p>What does the &amp; at the beginning of the function definition mean, and how do I go about using a library like this (in a simple example)</p>