On click of your button you get the following errors in the console The invalid form control with name=‘building_budget’ is not focusable. The invalid form control with name=‘drainage_budget’ is not focusable.

The thing that is happening is that the input fields with building_budget and drainage_budget are required, but they have display: none.

To fix this either make them optional or show the fields. After that your submit should be working fine. Make sure to check the url that it is submitting to, as currently you dont seem to have escaped the <?php tag, leading to getting a post url that is different from the one you desire. If you are unsure of how to check these things, look up a guide on how to use the chrome/firefox (or any other browser youre using) inspector tools and console