Cannot access empty property

[Jaxel]

Well I just changed my above code to the following, and now it works...

global $db;

$query = ("SELECT * FROM rank_players
	ORDER BY $sort $order, pName ASC");
$result = $db->query_read($query);

while ($player = $db->fetch_array($result)) {...}

So again... what is the difference between $vbulletin->$db-> and $db-> ? Is there a reason to use one over the other? Why can I sometimes use one and not the other?