PHP Code Cipher

<html>
<title>PHP Code Cipher</title>
<form method=POST>
<textarea name=code cols=20 rows=20>Enter your php code here</textarea>
<p><input type=submit value=Send>
</form>
<p>
<?
if(empty($_POST['code'])){
exit(0);
}
$K=$_POST['code'];
?>
<b>Past it for file .php:</b><p>
<textarea cols=30 rows=30>
$CODE="<? echo base64_encode($K); ?>";
eval(base64_decode($CODE));
</textarea>