[nuk3]

Originally Posted by Adib

Yes, I'd like to know this as well. Doesn't vb have a built in function to do this? I'm very hesitant of making a database call to vb's database if I don't have to.

In private.php:

// ###################### Start pm update counters #######################
// update the pm counters for $vbulletin->userinfo
function build_pm_counters()
{
	global $vbulletin;

	$pmcount = $vbulletin->db->query_first("
		SELECT
			COUNT(pmid) AS pmtotal,
			SUM(IF(messageread = 0 AND folderid >= 0, 1, 0)) AS pmunread
		FROM " . TABLE_PREFIX . "pm AS pm
		WHERE pm.userid = " . $vbulletin->userinfo['userid'] . "
	");

	$pmcount['pmtotal'] = intval($pmcount['pmtotal']);
	$pmcount['pmunread'] = intval($pmcount['pmunread']);

	if ($vbulletin->userinfo['pmtotal'] != $pmcount['pmtotal'] OR $vbulletin->userinfo['pmunread'] != $pmcount['pmunread'])
	{
		// init user data manager
		$userdata =& datamanager_init('User', $vbulletin, ERRTYPE_STANDARD);
		$userdata->set_existing($vbulletin->userinfo);
		$userdata->set('pmtotal', $pmcount['pmtotal']);
		$userdata->set('pmunread', $pmcount['pmunread']);
		$userdata->save();
	}
}

Give that a whirl.