public function movePageDisplayOrderToSibling(Page $c, $position = 'before')
    {
        $myCID = $this->getCollectionPointerOriginalID() ?: $this->getCollectionID();
        $relatedCID = $c->getCollectionPointerOriginalID() ?: $c->getCollectionID();
        $pageIDs = [];
        $db = Database::connection();
        $r = $db->executeQuery('select cID from Pages where cParentID = ? and cID <> ? order by cDisplayOrder asc', [$this->getCollectionParentID(), $myCID]);
        while (($cID = $r->fetchColumn()) !== false) {
            if ($cID == $relatedCID && $position == 'before') {
                $pageIDs[] = $myCID;
            }
            $pageIDs[] = $cID;
            if ($cID == $relatedCID && $position == 'after') {
                $pageIDs[] = $myCID;
            }
        }
        $displayOrder = 0;
        foreach ($pageIDs as $cID) {
            $co = self::getByID($cID);
            $co->updateDisplayOrder($displayOrder);
            ++$displayOrder;
        }
    }