Theres plenty of forum spambots used for advertising (like xrumer) which sign up by automatically entering information into .php pages.

I'd buy that if it wasnt for the fact that it targets different forums and emails them (oddly enough if you google mine around you can find some webserver with xrumer files on it including a pretty big forum list) I'd buy it to test this.

Surely there must be something out there that targets a single php page?