$bozuk=array("Ş","İ","Ö","Ü");
$duzgun=array("S","I","O","U");
function caesar_seo($deger) {
global $bozuk;
global $duzgun;
$deger = iconv("UTF-8", "ISO-8859-9", $deger);
$deger=str_replace($bozuk,$duzgun);
return $deger;
}
#kullanimi
$yazi="ŞİÜÖ";
caesar_seo($yazi);