Login to the site by file

In one of my projects, which I did for the mass user, I needed to make a password recovery mode without using email-a. I thought for a long time how to do this and in the end the idea came up to create a login by file (token), having which the user can go to the site and change the forgotten password. You can download the finished script with comments here .
If you have any questions please write, I will try to answer them :)