How to properly implement authorization through VK?

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Hello again) I figured out the problems of obtaining a token and other things. I didn’t understand one thing - how it all should be done correctly.
The VK API has so many redirects, I got confused in them. How to store user data and remember it on the site?
Now my structure is as follows:
There is an index, there is a link "authorize through VK". It leads to auth_user.php, where authorization takes place and a request for rights, then a redirect to get_token.php, where I get an access_token using the code that came. How to do it further, or how to redo it so that it is straight?