sending email to php script

A while ago an email came through here about how to parse out email message from a php script. The thing that was mostly of interest to me is the ability to send an email to a php script, I guess through a sendmail alias? I asked how to accomplish this, and never saw an answer come through. So I'd like to ask again :o) Does anybody know what would be required or necessary to send an email to an address that would run a php script?