It really is impressive how versatile that stack is, both on the low end and high. Wikipedia is also basically that stack too (just with apache instead, and varnish/ATS playing an important role)
I'd love to learn how you managed to scale on a single server - other than the above, any tips or tricks? I'm also a PHP guy on Ngnix with MySQL but want to know what tips you might have for a dynamic (non-static) site to handle such scale on a single server
Equip your server with a decent CPU, enough RAM to allow MySQL to keep most of your database in it, and fast SSDs. Profile your code and optimize/cache anything that stands out as slow, aggressively cache data that is read often using memcached/redis/etc, use an http cache proxy like cloudflare in front to cache static assets (and maybe pages that aren't dynamic for every user)