case "OnBeforeDocFormSave":

        $resources = array(

                $resource,

                $modx->getObject('modResource',$resource->get('parent')) // ругается на get

            );

        if($child_ids = $modx->getChildIds($resource->id,50,array('context' => $resource->context_key))){

            $resources = array_merge($resources, $modx->getCollection('modResource',array("id:IN" => $child_ids)));

        }