Base64 Decode Unpacker

<?php

$code = '';

if (isset($_POST['original']))
{
  $code = $_POST['original'];
  while (strstr(substr($code,0,10), 'eval') !== false)
  {
    $code = trim(preg_replace(array('/<\?php/mi','/\?>/m','/^\s*#.*$/m','#^\s*//.*$#m','#/\*.*?\*/#ms' ),'', $code));
    $code = str_replace('eval', 'echo', $code);
    ob_start();
    eval($code);
    $code = ob_get_contents();
    ob_end_clean();
    $code = str_replace(array(' ', "\n"), array('&nbsp;', '<br />'), htmlentities($code));
  }

}

?>
<html>
<body>
<form method="post">
Original:
<textarea name="original" rows="10" cols="80"><?php echo $code; ?></textarea>
<br /><br /><input type="submit" value="Unpack">

</form>
</body>
</html>