How to make a data handler?

Question

PHP

Need help, there is a ready-made online store on bitrix. When a user registers on the site, he enters his personal data there. After registration, the user logs in, then selects the product he needs, throws it into the basket, then clicks on the checkout button and a form appears where you need to enter your data, i.e. full name, address, phone number, etc., although the user is already entered your details during registration. How to make a data handler so that the data that was entered during registration is automatically pulled into the required form when placing an order. I just have never encountered this, what should I do, where should I look for among thousands of files?

Answer 1

From the session or from somewhere where Bitrix globally stores the user, get the user id, go to the database, get the data, substitute it into the inputs.

Answer 2

When a user registers on the site, he enters his personal data there.

Thus, you simply lose users who are not going to fill out questionnaires without a real need. And in addition, you get as the data that you were going to shove into the order - "Red Square, d. 1 k. 1. Lenin Vladimir Ilyich."
PS And so Bitrix has user profiles (multiple, because he can place an order not only for himself, but also for his parents, for example).