<?php
$fatura = $_GET['fiyat'];
$vergi = 1.18;
$vergiharic = $fatura / $vergi;
$vergitutari = $fatura - $vergiharic;

echo "Fatura Tutari: ".number_format($fatura,2)." YTL <br>";
echo "%18 KDV: ".number_format($vergitutari,2)." YTL <br>";
echo "Genel Toplam: ".number_format($fatura,2)." YTL <br>";

?>