[assassingod]

What you are doing isn't a query

use;

$countposts=$DB_site->query_first('SELECT COUNT(*) AS posts FROM post');
$totalposts=number_format($countposts['posts']);

$countthreads=$DB_site->query_first('SELECT COUNT(*) AS threads FROM thread');
$totalthreads=number_format($countthreads['threads']);

$countmembers=$DB_site->query_first('SELECT COUNT(*) AS users,MAX(userid) AS max FROM user');
$totalmembers=number_format($countmembers['users']);