php türkçe karakter replace sorunu

<?
$degisken = iconv("ISO-8859-9", "UTF-8", $_GET['adr']);
 
if(isset($degisken)){
function phpexpert($php){
$php=str_replace("-"," ",$php);
$php=str_replace("ç","c",$php);
$php=str_replace("ı","i",$php);
return $php;
}
echo phpexpert($degisken);
}
?>