<?php		    
$q = new Doctrine_Query();
$q->select('p.id, p.description')
  ->from('Product_Extras p')
  ->where('p.Product.item_code = ?');

$ret = $q->fetchOne(array($product_id));

if (!$ret) {
  

} else {
  $ret->description = $this->getRequestParamater('description');
}