Heresy! Combining Type Systems with PHP

on YouTube ↗44m

" summary

Explains how Hack actually puts a strong, static type system on PHP, with concrete mechanisms like unresolved types, fake locals, flow-sensitive tracking and a typechecker built atop HHVM that uses fork+mmap and a shared lockless hash table for parallelism. Describes incremental mode that avoids full rebuilds and the practical result: conversion of tens of millions of lines of code into Hack running on facebook.com since 2013, including the performance tradeoffs and cases that still fail or slow.

AI-written summary · about

" chapters (11)

1. 0:00Introduction
2. 8:19To keep in mind
3. 10:20Scoping
4. 17:27Flow sensitivity
5. 20:33Integration
6. 22:38Loop fixed point
7. 23:54Intersection types
8. 27:37Multithreading
9. 29:55Shared lockless hash table
10. 35:57Incremental mode client and server
11. 38:36Conclusion

" related talks

• 43mFrom PHP to Hack as a Stack and BackTimothy Chandler · PHPConf.Asia 2016
• 31mPHP to Hack, an incrementally typed Adventure at SlackScott Sandler · International PHP Conference Spring 2019
• 42mInclude Hack - HHVM - PHP++Sara Golemon, Paul Tarjan · OSCON 2014
• 54mHHVM, the new PHP?Stefan Priebsch · International PHP Conference Spring 2014
• 52mHHVM: the alternative PHP RuntimeSebastian Bergmann · International PHP Conference Spring 2014
• 30mConvert Your PHP Code to HackJosh Watzman · Hack Developer Day 2014
• 44mScaling with HipHopSara Golemon · PHP UK Conference 2013
• 59mPHP's type system dissected?Gina Peter Banyard · PHP UK Conference 2023