Hack: a new programming language for HHVM

What this post added

Introduced Hack, a new programming language for HHVM that interoperates seamlessly with PHP. Hack reconciles the fast development cycle of PHP with the discipline of static typing, incorporating features like generics, nullable types, type aliasing, and runtime enforcement of types. It also includes Collections for type-safe array alternatives and lambda expressions for concise closures. A key innovation is an instantaneous type checker that runs as a local server, providing sub-second feedback during development. The post also details the migration process and tools developed to convert PHP codebases to Hack, emphasizing its gradual typing nature and coexistence with PHP.