FB's primary reason for creating Hack was to add type-safety to PHP code. They spoke about how PHP was great for the fast development cycle, but would benefit from more structure if the created codebase was to become long lived. So the new Hack code is the same PHP code, only with types (and the implied benefits such static analysis, optimisations, etc).
Incidentally, this is also why FB created Flowtype - the lack of types is a massive boost during the code's youth, and a massive burden from early adulthood and onwards. Hack/Flow are a clever way to bridge the gap between typed and nontyped languages.
Incidentally, this is also why FB created Flowtype - the lack of types is a massive boost during the code's youth, and a massive burden from early adulthood and onwards. Hack/Flow are a clever way to bridge the gap between typed and nontyped languages.