public function movePageDisplayOrderToBottom()
    {
        // find the highest cDisplayOrder and increment by 1
        $db = Database::connection();
        $mx = $db->fetchAssoc('select max(cDisplayOrder) as m from Pages where cParentID = ?', [$this->getCollectionParentID()]);
        $max = $mx ? $mx['m'] : 0;
        ++$max;
        $this->updateDisplayOrder($max);
    }