public function setup_users() {
        global $SESSION, $DB;

        $this->userwheresql = "";
        $this->userwheresql_params = array();
        if (isset($SESSION->gradereport['filterfirstname']) && !empty($SESSION->gradereport['filterfirstname'])) {
            $this->userwheresql .= ' AND '.$DB->sql_like('u.firstname', ':firstname', false, false);
            $this->userwheresql_params['firstname'] = $SESSION->gradereport['filterfirstname'].'%';
        }
        if (isset($SESSION->gradereport['filtersurname']) && !empty($SESSION->gradereport['filtersurname'])) {
            $this->userwheresql .= ' AND '.$DB->sql_like('u.lastname', ':lastname', false, false);
            $this->userwheresql_params['lastname'] = $SESSION->gradereport['filtersurname'].'%';
        }
    }