$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];
$subject = $_POST['subject'];
$ip = $_SERVER['REMOTE_ADDR'];

if(!preg_match("/^[A-Za-z0-9]+$/", $name) && !preg_match("/^[A-Za-z0-9]+$/", $message) && !preg_match("/^[A-Za-z0-9]+$/", $subject)){
    echo "Lütfen Türkçe Karakter Kullanmayınız !";
}
else{
    $content="Gonderen: $name n E-Mail: $email n Mesaj: $message n Ip: $ip";
    $recipient = "info@xxxxxxx.net";
    $mailheader = "From: $email rn";
    $mailheader.= "Content-Type: text/html; charset=UTF-8";
    mail($recipient, $subject, $content, $mailheader) or die("Hata!");
    echo "Mesajınız gönderildi. Teşekkür ederim.";
}