HHVM is currently gaining popularity at quite a pace, and it's a pretty exciting time for PHP runtimes. Have you ever wondered what is going on beneath this slick and super-speedy engine? I wondered that myself, so I dived into the internals of HHVM, discovering a treasure trove of awesome stuff. In this talk, I'll show you how HHVM itself works with a guided tour of the codebase, demonstrating how it all pieces together. I'll also show you a couple of ways to write your own incredible HHVM extension. You don't need to know C++ to understand this talk - just PHP language knowledge is enough.