Login to the site by file

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