encrypted hidden value in a hyperlink

[scorpio22]

hi everyone, i am working on a project, where when a user registers, he would be provided with a link which he can give to anyone and ask them to register. once this new user, uses that link to register, he will be automatically assigned certain points, that was set by the manager while he was registering. i do want to use the POST, GET functionality, because the points value will be clearly seen on the hyperlink and if edited would give the user unlimited points. i want to know if there is any way i can encrypt it or provide a hyperlink is such a format that any user who logs in with that link will get the points set by that manager. how can i achieve this? i am using php and mysql.