Including header and pulling from database

Hey, I'm currently building up the main section of my website. I wondering if it is possible to include the xenforo header.

Example (Universal header style)
<?php include_once "PATH TO XENFORO HEADER.php"; ?>

Blah blah blah, main part of website

Does Xenforo use this system? Something else? or is it impossible without modifying a bunch?


How would I use the existing Xenforo user database with the rest of my website. How would I be able to get a login form that I create, to pull the information from the database?

Thanks for the help... hopefully those questions make sense