PHPBB debug interfering

Hello, i´ve trying to integrate wordpress into my existing site but phpbb is interfering wordpress. It´s because I have the phpbb login/logout system intergated in my site and I´m checking users login at the begining of my index page in this way:

—————————————————-
$login = false;
define(‘IN_PHPBB’, true);
$phpbb_root_path = ‘/web/htdocs/xxxx/xxx/Forum/’;
include($phpbb_root_path . ‘extension.inc’);
include($phpbb_root_path . ‘common.’.$phpEx);
//
// Start session management
//
$userdata = session_pagestart($user_ip, PAGE_INDEX);
init_userprefs($userdata);
//
// End session management
//
if($userdata[‘session_logged_in’])
{
$login=true;
}
———————————
and then I´m requiring wordpress to show the articles into my existing index page:
require(‘./articulos/wp-blog-header.php’);
<div id=”main-content”>
….
….
</div><!– close:main-content –>

But I get the phpbb debug mode instead of the worpress into my index.
I´ve tried to add the wordpress require before the phpbb login code but I get this error: “Fatal error: Cannot redeclare get_userdata() (previously declared in /web/htdocs/xxxx/xxx/articulos/wp-includes/pluggable.php:121) in /web/htdocs/xxxx/xxx/Forum/includes/functions.php on line 176”

So it seems that the function get_userdata() is the problem.
What can I do?

Thanks a lot.