public function get_export_params() {
        $itemids = array_keys($this->columns);
        $itemidsparam = implode(',', $itemids);
        if (empty($itemidsparam)) {
            $itemidsparam = '-1';
        }

        // We have a single grade display type constant.
        if (!is_array($this->displaytype)) {
            $displaytypes = $this->displaytype;
        } else {
            // Implode the grade display types array as moodle_url function doesn't accept arrays.
            $displaytypes = implode(',', $this->displaytype);
        }

        if (!empty($this->updatedgradesonly)) {
            $updatedgradesonly = $this->updatedgradesonly;
        } else {
            $updatedgradesonly = 0;
        }
        $params = array('id'                => $this->course->id,
                        'groupid'           => $this->groupid,
                        'itemids'           => $itemidsparam,
                        'export_letters'    => $this->export_letters,
                        'export_feedback'   => $this->export_feedback,
                        'updatedgradesonly' => $updatedgradesonly,
                        'decimalpoints'     => $this->decimalpoints,
                        'export_onlyactive' => $this->onlyactive,
                        'usercustomfields'  => $this->usercustomfields,
                        'displaytype'       => $displaytypes,
                        'key'               => $this->userkey);

        return $params;
    }