public function add_mform_elements(&$mform) {
        if (empty($this->type)) {
            return;
        }

        $mform->addElement('hidden', 'gpr_type', $this->type);
        $mform->setType('gpr_type', PARAM_SAFEDIR);

        if (!empty($this->plugin)) {
            $mform->addElement('hidden', 'gpr_plugin', $this->plugin);
            $mform->setType('gpr_plugin', PARAM_PLUGIN);
        }

        if (!empty($this->courseid)) {
            $mform->addElement('hidden', 'gpr_courseid', $this->courseid);
            $mform->setType('gpr_courseid', PARAM_INT);
        }

        if (!empty($this->userid)) {
            $mform->addElement('hidden', 'gpr_userid', $this->userid);
            $mform->setType('gpr_userid', PARAM_INT);
        }

        if (!empty($this->groupid)) {
            $mform->addElement('hidden', 'gpr_groupid', $this->groupid);
            $mform->setType('gpr_groupid', PARAM_INT);
        }

        if (!empty($this->page)) {
            $mform->addElement('hidden', 'gpr_page', $this->page);
            $mform->setType('gpr_page', PARAM_INT);
        }
    }