threadMarkAsRead() changes only last forum ID

[Jimmi08]

I do this in plugin - marking more than one forum as viewed

if (e_QUERY == 'mark_all_as_read')
{
	unset($u_new);
	$qry = 'WHERE thread_lastpost > ' . $lvisit;
	if ($rows = $sql->retrieve('forum_thread', 'thread_id', $qry, true))
	{   
		foreach($rows as $forumrow)
		{               
			$forum->threadMarkAsRead($forumrow['thread_id']);
		}                                     
    e107::redirect(e_REQUEST_SELF);
		exit;
	}
}

Because $currentUser['user_plugin_forum_viewed'] is not refreshed after adding one thread (I don't know how to call this), it's still the same and so only last thread is changed

	function threadMarkAsRead($threadId)
	{
		global $currentUser;                 
		$_tmp = preg_split('#\,+#', $currentUser['user_plugin_forum_viewed']);
		if(!is_array($threadId)) { $threadId = array($threadId); }
		foreach($threadId as $tid)
		{
			$_tmp[] = (int)$tid;
		}                            
		$tmp = array_unique($_tmp);              
		$viewed = trim(implode(',', $tmp), ',');   
   
		return e107::getDb()->update('user_extended', "user_plugin_forum_viewed = '{$viewed}' WHERE user_extended_id = ".USERID);
	}