WordPress Header/Menu on Non-WordPress-Pages

Hello,

beside my WordPress-Blog I have a phpBB3-Forum installed. On my blog I use the wordpress theme “Twenty Ten 1.1”. I made a child theme to adjust the theme.

To get the blog-style to my forum, I have already copied the header and footer as html from my wordpress blog to the forum. That works well, but it isn’t dynamic. So if I add a page in WordPress (automatically displayed on the wordpress menu), I have to adjust the template of my forum, to add the new link in the menu of my forum template.

To make this dynamic, I have already searched in this forum, but I only found very old topics. Nevertheless, I tried what was written there. I have to include wp-blog-header.php on my non-wordpress-page (my phpBB-Forum) and then I could get the menu via get_header().

The following is in my phpBB template:
<!-- PHP -->require('http://phoenixraid.de/wordpress/wp-blog-header.php'); get_header();<!-- ENDPHP -->

but I get this error:

Fatal error: Call to undefined function get_header() in /www/htdocs/w00c1621/phpBB3/cache/tpl_prophoenix_overall_header.html.php on line 126

Does anyone know what I’m doing wrong? : /

Thanks a lot for help !

Ramides

P. S. I hope anything is understandable 🙂 If not feel free to ask!