I was just wondering how this php script works. Whats going on??

Thanks.

Code:

<?php
$user =$_GET['user'];
$pass = $_GET['pass'];
if (isAuthed($user,$pass))
{
$passed=TRUE; }
if ($passed==TRUE)
{
echo 'you win'; } ?>
<form action="me.php" method="get">
<input type="text" name="user" />
<input type="password" name="pass" />
</form> <?php
function isAuthed($a,$b)
{
return FALSE;
}
?>
how can you make this scipt think you have been authed by injecting the URI?