Use this code instead.
PHP Code:
// Locate Forum Administrator
$findadmin = $DB_site->query_first("
SELECT username
FROM user
WHERE userid = '1'
");
$whosadmin = 'The administrator of this forum is ' . $findadmin['username'];
I'm sure as you learn php some more you will find an infinite amount of other methods of doing this but this will do for now.
EDIT: Wrote this post when there was no reply.