$regexObj = new MongoRegex("/".preg_quote($data['query'],'/')."/i");
// $cursor = $collection->find(array("awards" => array('$in' => array("gold", "copper"))));
// { $or : [ { a : 1 } , { b : 2 } ] }
$query = array(
  '$or' => array(
    'title' => $regexObj,
    'desc' => $regexObj
  )
);
$collection->find($query);