MyBB Community Forums

I'm trying to put last poster avatar in Forumlist...

i change code in index.php

$query = $db->query("
		SELECT f.*, fr.dateline AS lastread
		FROM ".TABLE_PREFIX."forums f
		LEFT JOIN ".TABLE_PREFIX."forumsread fr ON (fr.fid=f.fid AND fr.uid='{$mybb->user['uid']}')
		WHERE f.active != 0
		ORDER BY pid, disporder
	");

to

$query = $db->query("
		SELECT f.*, fr.dateline AS lastread, lp.avatar
		FROM ".TABLE_PREFIX."forums f
		LEFT JOIN ".TABLE_PREFIX."forumsread fr ON (fr.fid=f.fid AND fr.uid='{$mybb->user['uid']}')
		LEFT JOIN ".TABLE_PREFIX."users lp ON (lp.uid=f.lastposteruid) WHERE f.active != 0
		ORDER BY pid, disporder
	");

if i put {$forum['avatar']} in forumbit_depth2_forum_lastpost.
ok work... appear ./uploads/avatars/avatar_xxxxxxxxxxxxxx

so I make plugin...

$plugins->add_hook("build_forumbits_forum", "avatar_forum");

function avatar_forum(&$forum) {
	global $mybb, $forum, $forum_lpavatar;

    if(!$forum['avatar']) {
     $forum_lpavatar = "<a href='member.php?action=profile&uid={$forum['lastposteruid']}'><img src='images/default_avatar.gif' alt='' title='{$forum['lastposter']}' /></a>";
	 }
	 else
	 {
	 $forum_lpavatar = "<a href='member.php?action=profile&uid={$forum['lastposteruid']}'><img src='{$forum['avatar']}' alt='' title='{$forum['lastposter']}' />";
	 }
}

so...
if i put {$forum_lpavatar} in forumbit_depth2_forum_lastpost this not work...

why?