Good day!
This: the service is data which can give data through your API. Data
is not static.
Problem: we do third-party app which has to show different selections of the user. The collections are displayed and updated in real time.
Do I understand correctly that in this scheme we need to have a backend written in, say, PHP. And the user interface is written in JS.
Accordingly, the user selects what he wants to, JS makes a request to our backend, the backend sets the authorized server connection data and outputs them to the client.

Questions: we don't "get" if you make a backend in PHP? No problems with the scheme that I gave? With the requirement to maintain connectivity.
Perhaps the scheme has some mistakes?
Thank you.