[kh99]

OK, well, you can look at the part of newthread.php that starts with if ($_POST['do'] == 'postthread'). Basically it builds that $newpost array then calls build_new_post() to create the thread. If you want to look at a lower level of detail, build_new_post() is in includes/functions_newpost.php, that uses a data manager to do the work of writing to the database.

I understand what you're saying about not wanting to depend on newthread.php, but you're probably going to end up creating your own version of what it does, so you probably at least want to study how it works.