Konversi decimal to octal

if (isset($_POST['decimal'])){
$des = $_POST['decimal'];
$original = $_POST['decimal'];
$oct = '';
if (preg_match('/[^0-9]/',$des)) {
die ("maaf. inputan salah bos!");
}
else {
while ($des > 0) {
$hasil=$des%8;
switch($hasil){
case 0: $oct.="0"; break;
case 1: $oct.="1"; break;
case 2: $oct.="2"; break;
case 3: $oct.="3"; break;
case 4: $oct.="4"; break;
case 5: $oct.="5"; break;
case 6: $oct.="6"; break;
case 7: $oct.="7"; break;
case 8: $oct.="8"; break;
case 9: $oct.="9"; break;
case 10: $oct.="A"; break;
case 11: $oct.="B"; break;
case 12: $oct.="C"; break;
case 13: $oct.="D"; break;
case 14: $oct.="E"; break;
case 15: $oct.="F";
default:break;
}
if($des/8 == 0){
$sisa=($des%8);
$des=$sisa;
}
else{
$sisa=($des/8);
$des=$sisa%8;
}
}

$result = strrev($oct);
echo "bilangan $original (desimal) dalam octal adalah $result.
Back to the script";
}
}
else {
?>

result:

jika di konversi ===>