OH! Now I understand what you mean. You confused me with your comments …
To do what your example site is doing, there is no email involved at all. All you need is an upload script, and a customized form. I’d just check Hotscripts.com for an upload script in the language of your choice, and then just customize the form to your liking.
Uh, ok … let me google it for you.
There it is, from “scratch”. Frankly I think it might be a lot easier and quicker to use an existing script, but you wanted a “DIRECT” link on “creating” such a thing, so there you go.
I think part of what is confusing us both here, is that you are assuming that example site you referenced is using the “form” like a formmailer to collect the files and attach them to an email that is then sent to the printer. If that is what you want to do, you need to write/obtain/modify an script to do that.
An “Ecard” application was mentioned only because some of them already do most of that, and since you mentioned “cards” and “front” and “back” I thought it would be a good place to start. For what I now understand you to mean, any good formmail script that supports attachments will do the job nicely. Do you need me to google that for you?
On the other hand, that is not what the example site you pointed to is doing. They are doing it in a much better way (in my opinion) by just providing a facility for their clients to upload files to their server. That only takes the kind of upload script the tutorial I linked you to is about, and it doesn’t rely upon email at all.
Either way will work, the choice of which way to go is yours to make: If you want to do it via email, search for a script that is a “formmail with attachments” script for an example on how to create what you need (or to just use); if you want to do what your example site did, the tutorial above shows you how to build it from scratch - all you have to do then is customize your form (though, again, plenty of these types of scripts are readily available if you decide a “pre-written” solution is preferable).