submit_draft_assignment.php

<?php

define('CLI_SCRIPT', true);
require_once('config.php');


$cmid = 16;
$users = [
    11,
];

require_once($CFG->dirroot . '/mod/assign/locallib.php');

[$course, $cm] = get_course_and_cm_from_cmid($cmid);
$context = \context_module::instance($cm->id);

$assign = new assign($context, $cm, $course);

foreach ($users as $userid) {
    $user = \core_user::get_user($userid);

    \core\session\manager::init_empty_session();
    \core\session\manager::set_user($user);

    $notices = [];
    $assign->submit_for_grading([
        'userid' => $user->id,
    ], $notices);
}