static function exists( $contentID, $languageID , $subscriptionType, $email = null, $enabled = false )
    {
      
        $emailString = '';
        if ( !is_null($email) )
        {
            $emailString = " WHERE email = '$email'";
        }
        $countArray = null;
        $db = eZDB::instance();
        if ( $enabled === false )
        {
            $countArray = $db->arrayQuery( "SELECT count(*) AS count" .
                                       " FROM ezcomment_subscription" .
                                       " WHERE " .
                                       " content_id = $contentID" .
                                       " AND language_id = $languageID" .
                                       " AND subscription_type = '$subscriptionType'" .
                                       " AND subscriber_id IN" . 
                                       "( SELECT id FROM ezcomment_subscriber" .
                                       "$emailString )");
        }
        else
        if ( $enabled === 1 || $enabled === 0 )
        {
          $enabledString = "enabled = $enabled";
          if ( $emailString != '' )
          {
              $enabledString = " AND " . $enabledString;
          }
          else
          {
              $enabledString = " WHERE " . $enabledString;
          }
          $countArray = $db->arrayQuery( "SELECT count(*) AS count" .
                                       " FROM ezcomment_subscription" .
                                       " WHERE" .
                                       " content_id = $contentID" .
                                       " AND language_id = $languageID" .
                                       " AND subscription_type = '$subscriptionType'" .
                                       " AND subscriber_id IN" .
                                       " ( SELECT id FROM ezcomment_subscriber" .
                                       $emailString .
                                       "$enabledString )" );
        }
        else
        {
            return null;
        }
        $totalCount = $countArray[0]['count'];
        if ( $totalCount === '0' )
        {
            return false;
        }
        else
        {
            return true;
        }
    }