PHP + Apache long wait time

I think your problem is simply your hard disk with it's access times. Apache can cache html-pages in memory, but php-scripts are not cached; the need to be executed every time again. Therefore the php interpreter is called and it reads the script from the hdd. This takes a lot of time. The most slowest thing on your server is your HDD. On my pc, there is an extreme difference between applications starting from my SSD and my HDD (the SSD is up to 10 times faster!). If your HDD works, then the latency for executing an php script may increase drastically.

Possible solutions: get an SSD (maybe a small one just for often accessed data such as scripts) and minimize script calls (and HDD accesses) on your server. Make sure, the filesystem is defragmented (usually done automatically). If your php-script creates often the same contents, try caching them into an html file.

This answer could also help you: https://stackoverflow.com/questions/4181865/apache-php-caching

HTML file you're testing is just a plain file, all that Apache has to do is do a few system calls (open, read) and then serve its content.

PHP OTOH is actually quite a "heavy" option: it's an entire interpreter (bytecode compiler?). And since you're using concurrent testing (-c) who knows how well the requests are multiplexed to it? This does not have to be apache problem at all, but rather PHP's problem.

What I'd do:

1. Switch to Apache MPM (multi-threaded in multiple processes).

2. Do sequential test (no multiple concurrent requests), compare.

3. Run valgrind or some such on apache process and see where most CPU time is spent (apache or PHP).

4. run the same test but serving this page via nginx. Since nginx is based on async model and very fast, then if you get similar results, PHP is the culprit.

5. Finally, you could install Zend Optimizer (30-day trial is free) or smth like this: https://github.com/zendtech/ZendOptimizerPlus.

Really, comparing serving a static file to dynamically generated webpage is sort of apples to oranges comparison. None of the typical solutions (Python mod-apache, Django, PHP, etc) are going to be very fast in this regard, at least when compared to serving a static file. Node.js is an exception perhaps, due to sort of "low level" programming webpage directly in async model.

P.S. you have not quoted php.ini content. Post it and/or tweak it.