The word “hack” is an integral part of Facebook’s culture, so it should come as little surprise that a programming language it developed for HHVM that integrates seamlessly with PHP, which it announced the open-sourcing of Thursday, is called Hack.
The social network said in a post on its engineering blog that it migrated its entire PHP code base to Hack over the past year, adding that the programming language “resolves the fast development cycle of PHP with the discipline provided by static typing,” while adding features from other, modern programming languages.