MyBB Community Forums

I want my website and my mybb board to be connected. I Googled and made the integration, and I'm able to get a username id, as long as I specify their ID, but nothing happens when I'm using the function as explained.

What I'm trying to do is verify a connection of one to the forums, via my website, and then show their name.

Here's my code, as well as my attempts to get a username:

PHP Code:
define('IN_MYBB', NULL);
require_once 'forums/global.php';
require_once 'forums/class.MyBBIntegrator.php';
$MyBBI = new MyBBIntegrator($mybb, $db, $cache, $plugins, $lang, $config); 

$user = get_user($uid);

while ($forum_user = mysqli_fetch_array($user))
{
echo $forum_user['username'];
}