Custom Template Hook

[TiKu]

Hi,

I want to add a template hook called 'above_header' right at the beginning of the 'header' template. So in the 'header' template I've added

{vb:raw template_hook.above_header}

.
This template hook shall be used by a plugin which hooks 'forumdisplay_start'. The code of the plugin is:

$forum = $vbulletin->forumcache["$forumid"];
$templater = vB_Template::create('ivwcode');
	$templater->register('forum', $forum);
$template_hook['above_header'] .= $templater->render();

The 'ivwcode' template currently consists of just the text "foobar".

Unfortunately the content of the 'ivwcode' template is missing in the generated HTML code. Why?

Regards
TiKu