title: PHP MongoDB update multiple fields with one query
body: <p>I've tried running this query:</p>
  
  <pre><code>$collection-&gt;update(
      array('_id' =&gt; 'mongoIDhere'),
      array(
          '$set' =&gt; array("parent" =&gt; 'data'),
          array("parents" =&gt; 'data')
      ),
      array("upsert" =&gt; true)
  );
  </code></pre>
  
  <p>But it will only update the second "set" parameter (which is array("parents" => 'data') ). When done in two separate queries these work fine, but together it doesn't - what gives?!</p>