PHP vBulletin ACL Integration

[Bob Meta]

Hi All, I am trying to print a user's login name from a PHP script or redirect them to the vBulletin login page so that vBulletin is the central authorization database. Nothing fancy:

<?php
$vb = new vbulletin(); //* this isn't real, i know, but it's what i'm looking for or something similar

if ( $loggedIn ) {
	print $userName;
} else {
	header( "Location: ...login url..." );
}
?>

Any pointers or suggestions are welcomed and greatly appreciated! Thank you!