themeUpdate.json.php

<?php
header('Content-Type: application/json');
global $global, $config;
if (!isset($global['systemRootPath'])) {
    require_once '../videos/configuration.php';
}
require_once $global['systemRootPath'] . 'objects/user.php';
if (!User::isAdmin()) {
    die('{"error":"' . __("Permission denied") . '"}');
}

$config = new Configuration();
$config->setTheme($_POST['theme']);

echo '{"status":"' . $config->save() . '"}';