php script that sends the user a link to complete validation process

hey... trying to find a quick php script/sample code/etc... that does validation for a user. basically, i want the admin to authorize a user via a form. i want the form to kick off an email to the user that will require the user to goto the link to complete the validation process. i've seen these before, but i can't seem to find an example now....!! any help would be appreciated. thanks bruce bedouglas@earthlink.net