static function Purge()
 {
     global $zdbh;
     global $controller;
     $numrecords = 0;
     $sql = "SELECT COUNT(*) FROM x_dns WHERE dn_deleted_ts IS NOT NULL";
     if ($numrows = $zdbh->query($sql)) {
         if ($numrows->fetchColumn() != 0) {
             $sql = $zdbh->prepare("SELECT * FROM x_dns WHERE dn_deleted_ts IS NOT NULL");
             $sql->execute();
             while ($row = $sql->fetch()) {
                 $delete_record = $zdbh->prepare("DELETE FROM x_dns WHERE dn_id_pk = :dn_id_pk");
                 $delete_record->bindParam(':dn_id_pk', $row['dn_id_pk']);
                 $delete_record->execute();
                 $numrecords++;
             }
             self::$purged = $numrecords;
         }
     }
 }