public function get_requester() {
        global $DB;
        static $requesters= array();
        if (!array_key_exists($this->properties->requester, $requesters)) {
            $requesters[$this->properties->requester] = $DB->get_record('user', array('id'=>$this->properties->requester));
        }
        return $requesters[$this->properties->requester];
    }