Combining Type Systems with PHP: Hack's Approach

Explore the technical intricacies of Hack, Facebook's dialect of PHP, in this comprehensive conference talk. Delve into the implementation of a strong, static type system onto a dynamic, untyped language like PHP. Gain insights into the type system's design and the static typechecker that enforces it, with a focus on maintaining PHP's productivity advantages. Learn about unresolved types, fake locals, integration techniques, and chaining. Examine practical examples, including intersection types and error handling. Discover how Hack addresses scaling challenges through multithreading, shared memory regions, and a client-server model for dependency tracking and rechecking. Enhance your understanding of modern PHP development and type system integration in this in-depth technical presentation.

Introduction
Overview
What is Hack
PHP
PHP Code
Pragmatism
Who are we
The hack type system
Things to keep in mind
Unresolved types
Fake locals
Integration
Chaining
Feature Loop
Example Code
Intersection Types
Error Messages
Type Error
Invalid Return Type
Scaling
Multithreading
Shared Memory Region
Invariants
Clientserver model
Tracking dependencies
Rechecking dependencies
Conclusion