function tosize($bytes,$prec=2){

    $rank=0;

    $size=$bytes;

    $unit="B";

    while($size>1024){

        $size=$size/1024;

        $rank++;

    }

    $size=round($size,$prec);

    switch ($rank){

        case "1":

            $unit="KB";

            break;

        case "2":

            $unit="MB";

            break;

        case "3":

            $unit="GB";

            break;

        case "4":

            $unit="TB";

            break;

        default :

    }

    return $size." ".$unit;

 }