How to redirect back?

Question

PHP

I have product pages, and at the bottom there are comments to them, and I need that if the user is not registered, a link to the login page pops up, and that after the user logs in, he is redirected back to the same product page. Please tell me how to make such a redirect?
P.S. I want to note that the usual WordPress redirect after authorization does not suit me, because I do not want to change the general behavior, but only locally on the product pages

Answer 1

1. When you click on the link, write down cookies with the address.
2. after logging in, redirect back to the address with cookies.
3. delete cookies.