foreach (range(1, 5) as $i) {
    try { // запуск параллельно
        $spec = [0 => ["pipe", "r"], 1 => ["pipe", "w"],];
        $i = sprintf("%03d", $i);
        $cmd = "wget https://k7.org/2-$i.mp3";
        $proc = proc_open($cmd, $spec, $pipes);
    } catch (\Exception $e) {
        Log::error($e);
    }
}