static function Retrieve($id)
 {
     if (!$id) {
         return null;
     }
     $entity = new Entity();
     $query = "SELECT * FROM #__contact_details WHERE id = ?";
     $object = $entity->GetFirstResult($query, $id, __CLASS__);
     if (!$object) {
         return null;
     }
     $object->user = User::Retrieve($object->user_id);
     return $object;
 }