How to check a user for VK API authorization?

Question

PHP

I called the user authorization method (not on the server side) () vk api
Tell me how to make the user, when not authorized, write to him "Login through VK", and when authorized, he writes "Hi"

Answer 1

I guess you need https://vk.com/dev/Login

Answer 2

It is very similar to the fact that the question is about sessions. Should you write "log in with VK" on your site?