[BlueOnyx:09117] php stopped working

[bob richards]

At about 6am today my php started downloading the php files rather
than executing them.
It's happening across all sites.
The admin is working fine.

I added a
LoadModule php5_module modules/libphp5.so
to http.conf and got a
[warn] module php5_module is already loaded, skipping
so it appears php is getting loaded.

I've compared my http.conf and vhosts files to a good blue onyx and
everything seems the same.

I'm guessing something got updated via yum that broke it.

Any ideas on where to look?

Thanks.