> With mod_php, every Apache process has the PHP engine embedded in it, even if PHP isn't needed, e.g., to serve a request for a .css file. When Apache gets a bunch of requests for flat files, it forks all those processes and fills up RAM with copies of the PHP engine that aren't used. That's not only wasteful, but it dramatically increases the chances that you'll run out of memory. You can limit the number of Apache children of course, but you'll see timeouts sooner when you get a traffic spike.
Yes, that is true. But most high-traffic websites will cache static files such as CSS files and images, using a reverse proxy (e.g. Varnish, a CDN, or usually both). So I don't think this is a real problem, most of the time (99.9%?), a request for a static file will not hit Apache.
I'm not saying mod_php is better for all scenarios, of course, but I think it can be ok.
It's simple and there is less overhead. Since PHP runs directly within the Apache process, there is no need for inter-process communication (no TCP, no sockets), reducing the overhead. This can lead to lower latency for individual requests.