Hello, oldnewbie,
I reviewed the document contained in the page you are adressing, it basically proposes three methods for making a flash background transparent (by the way, and answering your question, I do want a php page behind the flash embedded object to be visible). I tried the three methods and none of them work.
I'm not a flash programmer, and maybe there are important facts when editing a movie that I'm omitting.
Also I was wondering whether the failure is due to the fact that I'm compiling the movie using the Flash test version.
Please help, and thank you!