Posting to a remote form assistance required

I have a simple form on a Hubspot system. I use the details on HubSpot for marketing purposes, so I do need a HubSpot form instead of a normal form on my platform.

This is my setup:

1. www.thedomain.com -- this is out website running on HubSpot
2. app.thedomain.com -- this runs our Php platform

On the HubSpot site (www.thedomain.com) I have a form with the following fields that works 100% to capture user date.

1. First Name
2. Last Name
3. Email Address
4. Username (this is not really being used in HubSpot)

On Submit, I want to have a javascript that takes the completed fields and posts them on a similar form on my App (app.thedomain.com). The fields must exactly be the same as the ones completed on HubSpot.

In short, when you click submit and there are not errors, you are redirected to the app.thedomain.com and the form there is pre-populated - all you do is click "Sign Up" again.

I need some guidance in the right place. I can run javascript/jquery on HubSpot.

via Chebli Mohamed