TANSTAAFL!! sleipnir you put me on the right track.
My testing may be of use to future programmers looking for the same indicator:
I wrote a little php routine to list all the members of $_SERVER. Nothing useful showed up except the server port (which was 80) as I had invoked the program using http.
When I tested the same routine using https, the port changed to 443, so I have an indicator. THEN I noticed that there was a new element called HTTPS (it did not show up in the first test not having been set) with a value of "on".
This is a much more direct test and it works well.