php mail form with predefined subject

I am in need of a mail form script which has the subject line filled in for the user....Here's what I mean.... Let's say I have a webpage. On the web page is a picture of a truck, maybe a 1999 Ford F150. If the user clicks the pic, he/she is taken to a brief description of the truck. On the description page is a button which says "email for more info". If the user clicks this button he/she is taken to a page which is a mail form, with the subject being something like, "Requesting information on 1999 Ford F150" I guess what you could say, in a way, is that I want to have a mail form, with the subject set according to where the user is coming from...sort of, I guess... Can anyone point me to some example code on how to do this? Or an archive of php mailform scripts? Thanks, Ed