How to insert the ID of the current user into the link?

Question

PHP

Hello!
No one will tell you how to make it so that you can add the ID of the Vkontakte user who clicks on the link to the link?
Let's imagine that I have ID 1, and in the post, clicking on the link, it should be like site.com?user_id=1
What can you tell me, gentlemen?
Thanks for the help.

Answer 1

How the site can find out the user id in the social. networks?