PHP publishing is working? How you upgrade to SnowLeopard? With FM Server installed or not?
I suppose - something wrong is happen with Apache webserver.
Backup everything necessary (TimeMachine), reinstall OS X (erase HD) and so on.
I have 2 such cases with my clients: update to SnowLeopard with FMS working. Apache "kaput".
To avoid long job I have done as I have described and they are happy until today. Anyway - 1/2 day was wasted...