Связь ajax php и javascript

elseif($action == 'loadtrack') {
    $row = $db->super_query("SELECT id, onserver FROM " . PREFIX . "_music WHERE id='{$id}'");
    $filename = basename($row['onserver']);
    $file = ($music->config['file_dir'].'/'.$filename);
    if(file_exists($file)) {
        $config['files_max_speed'] = intval($config['files_max_speed']);
        include_once ENGINE_DIR.'/classes/download.class.php';
        $downloadfile = new download($file, $filename, $config['files_force'], $config['files_max_speed']);
        $downloadfile->download_file();
        $db->query("UPDATE " . PREFIX . "_music SET down_num = down_num + 1 WHERE id='{$id}'");
        $db->close();
    }
    else {
        $server = $row['onserver'];
        @header("Location:{$server}");
    }
}

function loadtrack(id) {
    ShowLoading('');
    $.post(dle_root + "engine/modules/music/ajax/ajax.php", {action:'loadtrack', id:id}, function(data){
        HideLoading('');
        ???????
    });
    return false;
}