engelsystem/includes/model/UserGroups_model.php

<?php

use Engelsystem\Database\Db;

/**
 * Returns users groups
 *
 * @param int $userId
 * @return array[]
 */
function User_groups($userId)
{
    return Db::select('
            SELECT `Groups`.*
            FROM `UserGroups`
            JOIN `Groups` ON `Groups`.`UID`=`UserGroups`.`group_id`
            WHERE `UserGroups`.`uid`=?
            ORDER BY `UserGroups`.`group_id`
        ',
        [$userId]
    );
}