https://hizliresim.com/BjscRO
<head>
<title> Ödev5a_180102033</title>
<head>
<body>
<form action="" method="post">
E-Posta: <input type="text" name="post">
<input type="submit" name="tamam" value="GÖNDER">
</form>
</body>
</html>
<?php
$metin=$_POST["post"];
$a=explode("@","$metin");
echo "Kullanıcı Adı:<font color=red>$a[0]</font><br>";
?>