ctf题 找flag 求解？

Question

<?php
highlight_file(__FILE__);
include('../flag.php');
$user=$_GET['user'];
if(isset($user))
{
if($user === 'xatusec')
echo $flag1;
else
echo 'GET_GET_GET';
}
else
echo 'oh no';
?> oh no

Answer 1

?user=xatusec