/**
 * Retrieve object using using composite pkey values.
 * @param      string $ip
   @param      int $comment_id
   
 * @param      PropelPDO $con
 * @return     CourseCommentDig
 */
 public static function retrieveByPK($ip, $comment_id, PropelPDO $con = null)
 {
     $key = serialize(array((string) $ip, (string) $comment_id));
     if (null !== ($obj = CourseCommentDigPeer::getInstanceFromPool($key))) {
         return $obj;
     }
     if ($con === null) {
         $con = Propel::getConnection(CourseCommentDigPeer::DATABASE_NAME, Propel::CONNECTION_READ);
     }
     $criteria = new Criteria(CourseCommentDigPeer::DATABASE_NAME);
     $criteria->add(CourseCommentDigPeer::IP, $ip);
     $criteria->add(CourseCommentDigPeer::COMMENT_ID, $comment_id);
     $v = CourseCommentDigPeer::doSelect($criteria, $con);
     return !empty($v) ? $v[0] : null;
 }