This is the full code used to get the total post and thread count. You need to modify it for your own purposes.
PHP Code:
$totalthreads = 0;
$totalposts = 0;
if (is_array($vbulletin->forumcache))
{
foreach ($vbulletin->forumcache AS $forum)
{
$totalthreads += $forum['threadcount'];
$totalposts += $forum['replycount'];
}
}
$totalthreads = vb_number_format($totalthreads);
$totalposts = vb_number_format($totalposts);