customized php + G2

I write own php applicaion which call embed G2.
My folder structure is
/www/ (physical path)
/www/gallery2 (physical path)
I write own login.php file inside /www/ path which will call G2.
Following is my coding. I tried ok to call G2 via following code if $uid = ''
If I set $uid = 'admin', it will fail. Thanks.

$uid = '';

// initiate G2
$ret = GalleryEmbed::init(array('g2Uri' => '/gallery2/',
'embedUri' => '/login.php',
'activeUserId' => $uid));

Actually, I want to use customized php page which has login and password text box to login and vertify with own database and then notify G2 success or not. Is it correct method to do?