I'm looking to provide a one-click login link for users, after the order has been delivered, to gather feedback from them. Asking them to login is apparently too much effort.

I have a database table set up so far that contains a hashtag specific to them, and want to write a script to automatically log them in when they visit myreview.php?hashtag=32rhbb23jrhb29sdfiuetc

I'm having a difficult time understanding how to set their login cookie (or is it stored serverside?). Is this even possible?

I'm aware that there are security implications. It will be a one-time use (the user's hash is deleted from the one-click database table on first login). Anything else I should consider?