http://www.jblotus.com/2013/02/01/simply-scale-with-nginx-memcached-php-fpm-and-apc/

When I started programming in PHP, my hosting setup involved a cPanel installation with Apache and MySQL. This has been the de facto standard for many PHP developers and for the most part I don’t think any of that needs to change. I simply never had to deal with websites that got more than 10,000 visits a day. This all changed when I started work at my current job a few years ago. We sell an educational product that serves a predictable 15,000 requests per minute for 10+ hours/day, every day. Instead of Apache, we use nginx with PHP-FPM to handle this traffic. This is becoming a very popular setup for many companies with non-trivial traffic, but I have also found success with it in my small 256MB Ram VPS. For various reasons, nginx does a better job with memory and concurrent connection handling than Apache. In this post, I want to talk about some of the reasons you might want to go with this setup.