Pipe SMTP mail messages to a PHP file located on the server with all headers

[712011m4n]

So I have a client who needs something that would seem fairly easy but I cant seem to wrap my head around it.

The project idea is as stated:
-The server receives mail via "sendmail" .
-From what I hear sendmail allows you to pipe to a php
file on the server.
-Said PHP file then needs to parse through each message to determine where it came from and set conditions based on the subject line content.
-Say we have 3 conditions that could be met labeled as purchase types: Online, Mail Order, Phone.
-Depending on the purchase type the php script then databases the purchase accordingly based on its type.

That's really all I need to do but my issue is, I know nothing about send mail and its piping functionality because I use GoDaddy for my mail server needs(which sucks by the way) and GoDaddy doesnt let you see this so called "SendMail" file so I cant pipe to the php file.

I guess what I am asking here is, if my client knows where to plug in the PHP file in his sendmail configuration, should I just focus on working on the PHP file regardless of how the piping will occur?

Any ideas or help/guidance would be admired and appreciated.

Let me know please.

-Frosty