Need to make a general registration between forums XenForo and phpBB.
It's very simple: the user registrated the forum XenForo, and at the moment when the engine adds its entry into the database, there is an additional request to the other database (phpBB).
After talking with a support center, I was informed that the call to register in the file: \upload\library\XenForo\ControllerPublic\Register.php
It is the method: XenForo_ControllerPublic_Register:: actionRegister ();
That it is necessary to create an additional request to the other database.
Actually the question of how to form SQL query tools XenForo?