Firebase hosting has been excellent, up until now. It is very fast and very cheap. Alas, there is absolutely no access to any server-side activities such as you normally would with PHP. I'm using Opayo 3D Secure to process payments. Part of this involves showing an OPayo webpage inside an iframe to capture bank card details. This then returns another URL from a bank that issues a question to the card's account holder. When complete, the bank sends a POST message to my website with two parameters that I then use to complete the transaction. I can see these parameters in Chrome's Devtools but I have no idea how to access them using Javascript.
Here are the returned values (cres and threeDSSessionData):
It is not possible to use fetch() or XMLHttpRequest() to get the response. The URLs provided must be presented using iframes.
Obviously, Firebase Hosting is passing the HTTP headers and body back to the website, as can be seen from the Devtools, but how do I get hold of them?