@Jay_Emery
It sounds like you are wanting to use your own form that will submit to your server then the server will post to an Infusionsoft form. The issue with doing this is that it is the same method used by spam bots. As we improve our spam bot detection your script might not work. We suggest utilizing the API to add contact information into Infusionsoft as documented if the following places:
https://developer.infusionsoft.com/docs/rest/#!/Contact/createContactUsingPOST
https://developer.infusionsoft.com/docs/rest/#!/Contact/createOrUpdateContactUsingPUT
https://developer.infusionsoft.com/docs/rest/#!/Contact/updateContactUsingPATCH
https://developer.infusionsoft.com/docs/xml-rpc/#contact-create-a-contact
https://developer.infusionsoft.com/docs/xml-rpc/#contact-create-a-contact-and-check-for-duplicates
There is another thread about this which can be found here: Use curl to submit infusion legacy form