How to assign a city to a site visitor during repeated visits?

Question

Web traffic analysis

visitors to the direct come from different cities through tags
, i.e. at the first hit, I know what city they are from.
How to assign a city to a visitor while he roams the site
and how to assign a city to him if he left the site by closing the window, and then returned a few days later but through a direct link

Answer 1

The visitor is given a cookie when they first log in.
The city, browsing history with ip-addresses, etc. are stored in the sql-base for this cookie.