You might be able to get PHP files to run in your AIR app, but it would be exceedingly complicated. There's this project, PHP for Android, and perhaps you package that into a binary that you include with your APK, and address in Flash via a native extension.
It's a bit unusual to try to adapt a Flash+PHP client-server model app onto a phone, to be honest. You'll likely be forging your own path if you want to avoid rewriting the server logic in AS3.
“Who were you, Krilnon, and how did you know so much about AS4?”
The historian sighed as she gazed up at the sky and saw… not stars. A story.