How to connect the "join group" button and the database?

Question

JavaScript

Hello! How to implement such a script - On the site, after clicking on the "Join the VK group" button (widget from VK), the user who clicked this button, enter an entry in the database?
Thanks in advance!

Answer 1

Should the user who clicked this button write a record to the database?

I'm sorry, what? To bring to the user record in a DB?
In general, Vkontakte has a CallBack API that notifies your server about some events (the list of which you can find at the link above), as a result of which (events) you can add the desired entry to the database or

the user who clicked this button to enter the record in the database

or do something else like that.