Moodle 3.9 - Mod Menampilkan Nama Pengajar di Tampilan Course

/* modif untuk menampilkan nama pengajar di tampilan Course
   sisipkan pada \course\view.php setelah baris yg berisi kode echo $OUTPUT->header();
*/
// mulai mod menampilkan nama pengajar
    $teachers = $DB->get_records_sql("SELECT u.id as userid, u.id, c.shortname, u.username, u.firstname, u.lastname
                              FROM mdl_course c
                              LEFT OUTER JOIN mdl_context cx ON c.id = cx.instanceid
                              LEFT OUTER JOIN mdl_role_assignments ra ON cx.id = ra.contextid AND ra.roleid = '3'
                              LEFT OUTER JOIN mdl_user u ON ra.userid = u.id
                              WHERE cx.contextlevel = '50' AND c.id=".$course->id . ";");
    if ($teachers) {
            $html .= 'Pengajar/Pemateri: ';
        $html .= html_writer::start_tag('ul', array('class' => 'teachers'));
            foreach ($teachers as $teacher) {
                $name = html_writer::link(new moodle_url('/user/view.php',
                    array('id' => $teacher->id, 'course' => SITEID)),
                    $teacher->firstname . " " .  $teacher->lastname);
        $html .= html_writer::tag('li', $name);
        }
            $html .= html_writer::end_tag('ul');
        echo $html;
    }
//  akhir mod menampilkan nama pengajar