Rhandom wrote

Most likely they are using fastcgi to run their php or using a php bytecode caching mechanism.

and you wrote

Are you sure they have mod_php? Many shared hosts run PHP as CGI because they don't trust the security of mod_php in a shared environment.

No, I'm not sure. Really? PHP as CGI? I'd just assumed that mod_php was being used. Thank you both. The sites I've dealt with were pretty quick and were getting a fair amount of traffic, and since it was php, I'd just assumed that they running with mod_php. I'll have to make some inquiries to hosting providers. I'd be very curious to know if they're using fastcgi for php, and if I could take advantage of it using Perl.

Perhaps shared hosting setups offering fastcgi are more common than I'd thought?