The website that I created enables users to signup. When they register an account, a mail is sent to them.

In the mail, I wish to send them a link upon clicking of which enables them to login.

How can I do this?

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I was thinking on the following lines-

Upon user registration, generate a random query string and send it in the mail. In the users table keep a boolean variable depending upon whether the user has clicked or not (matching the querystring). How can I code the login page so as to 'read' the querystring in the browser?