Bulk cohort enroll

I want to enroll cohorts to courses in bulk (via cohort sync, not enroll users from a cohort). After reading the REST API documentation, I haven't found a way to do this. Therefore, I want to achieve it using a php script. This is what I have tried:

<?php
define('CLI_SCRIPT', true);

require_once('/var/www/moodle/config.php');
require_once($CFG->dirroot . '/lib/clilib.php');
require_once($CFG->dirroot . '/cohort/lib.php');
require_once($CFG->dirroot . '/enrol/cohort/lib.php');

$courseId = 205;
$cohortId = 167;

// Login
$systemcontext = context_system::instance();
$userid = 2; // user admin
$session = null;

// Enroll
$enrollmentPlugin = enrol_get_plugin('cohort');
$enrollmentPlugin->sync_cohort($courseId, $cohortId);

But it doesn't work as I don't know proper functions and methods. Can someone help me complete the script?

Moodle Version: 3.11
PHP Version: 7.4

You probably want to use something like

$studentroleid = $DB->get_field('role', 'id', array('shortname' => 'student'));

$course = get_course($courseid);

$cohortplugin = enrol_get_plugin('cohort');

if (!$cohortplugin->can_add_instance($courseid)) {
    // Display some error message?
    return;
}

$cohortplugin->add_instance($course,
    ['customint1' => $cohortid,
    'roleid' => $studentroleid]);

And I think you can add multiple cohorts to a single cohort enrol plugin - I haven't tried it but use an array for the customint1 parameter

$cohortplugin->add_instance($course
    ['customint1' => [$cohortid1, $cohortid2],
    'roleid' => $studentroleid]);

To create a cohort group using $fields['customint2'] == COHORT_CREATE_GROUP, check if the user has the required capability

$context = context_course::instance($course->id);
if (!has_capability('moodle/course:managegroups', $context)) {
    // Can't add a cohort group, display a message?
    return;
}