title: PHP Mongo Query NOT NULL
body: <p>Anyone know the syntax for writing a php-mongo query to use <code>NOT NULL</code>?</p>
  
  <p>I know how to do this when I query for <code>NULL</code>:</p>
  
  <pre><code>&lt;?php
  $cursor = $collection-&gt;find(array("someField" =&gt; null));
  </code></pre>
  
  <p>Is this even possible?</p>