Something that you don't see offered by cart systems is the possibility to electronically sign invoices. As far as I can tell on European soil this is even a legal requirement for a valid electronic invoice nowadays. What I mean is that an legally valid invoice is either printed on company paper and sent with the product or when the product is not tangible and we want to avoid snail mail, the on-line invoice should have the following characteristics (as far as I know):
1. The invoice should be electronically signed with a certified signature that is acceptable to the local authorities or tax office.
2. I think that the invoice is not allowed to change anymore after it is signed and time stamped.
3. In my country the local authorities offer a signature verification service and the signed invoice should be compatible with that. Also for the client's sake it should be easy for them to use this service.
My question is if there are developers or shop owners that are developing something in that direction? If there is any initiative I would like to know about it and may be I can contribute time, money, my input etc.
Would any of you know how to go about implementing something like that? To date I cannot find any open source PHP library. There are some references to an iText port to PHP but I did not find it anywhere, only rumors, a related getacoder project and even one that relates to Drupal. So the only open source solution would be by somehow using iText under Java and switch to a pure PHP solution when it becomes available?
every buyer has his own needs.