Facebook engineers Bryan O’Sullivan, Julien Verlaguet, and Alok Menghrajani have spent the last few years building a programming language unlike any other that Facebook uses to create its web-based system. The language is called Hack and the language's website says "Hack is a programming language for HHVM that interoperates seamlessly with PHP. Hack reconciles the fast development cycle of PHP with the discipline provided by static typing, while adding many features commonly found in other modern programming languages. Hack provides instantaneous type checking via a local server that watches the filesystem. It typically runs in less than 200 milliseconds, making it easy to integrate into your development workflow without introducing a noticeable delay." Hack is open source and available for you to use now. You can find out more on the hack.org website or in this post by Hacker News.