Can you test to see if you get a response from the web server, externally, either by IP address or domain name? Is the PHP hosted on the same machine as FMS?
If the web publishing engine is installed and running, php just points to that with an address to do it's thing, so if the PHP is on a externally hosted server, and that domain name changes, you will need to update the address in the php code as well.
The web server appears to be working both with IP and by name. The php is on the same machine (keep in mind that this computer has also had a fresh install of FMSA11.
If the php script is broken all together, it should not stop the web stuff from being setup, right?
FMS Web Publishing and sharepoint on SBS conflict and at some point one or the other will stop working. The only solution I've seen that will fix both is to completely re-install the OS.
SBS and FMS don't mix. They're officially unsupported, but in my opinion the installer should be modified so it won't let you install at all.