error("assignment ID was incorrect");
    }
    if (!($course = $DB->get_record('course', array('id' => $assignment->course)))) {
        error("Course is misconfigured");
    }
    $url->param('id', $id);
} else {
    if (!($assignment = $DB->get_record('assignment', array('id' => $a)))) {
        error("Course module is incorrect");
    }
    if (!($course = $DB->get_record("course", array('id' => $assignment->course)))) {
        error("Course is misconfigured");
    }
    if (!($cm = get_coursemodule_from_instance("assignment", $assignment->id, $course->id))) {
        error("Course Module ID was incorrect");
    }
    $url->param('a', $a);
}
$PAGE->set_url($url);
require_login($course->id, false, $cm);
require_capability('mod/assignment:grade', get_context_instance(CONTEXT_MODULE, $cm->id));
require dirname(__FILE__) . '/assignment.class.php';
$assignmentinstance = new assignment_uploadpdf($cm->id, $assignment, $cm, $course);
$action = optional_param('action', null, PARAM_TEXT);
if ($action == 'showprevious') {
    $assignmentinstance->show_previous_comments($userid);
} elseif ($action == 'showpreviouspage') {
    $assignmentinstance->edit_comment_page($userid, $pageno, false);
} else {
    $assignmentinstance->edit_comment_page($userid, $pageno);
}