HipHop VM: PHP on the metal

Joel Pobar (Facebook)
Location: D139/140 Level: Expert
Average rating: ****.
(4.22, 9 ratings)

The PHP programming language resists efficient execution. Like many other popular web languages, PHP offers programmers the conveniences of dynamic typing, and late binding for functions and classes. PHP also introduces a few distinctive challenges: its reference argument-passing semantics, and its exposure of reference-counting as the underlying implementation for storage management. Facebook’s HipHop VM (HHVM) is a new execution engine for PHP that combines ahead-of-time and just-in-time techniques to try save precious CPU cycles in the face of these challenges. Throughout the process of bringing HHVM to life, we’ve been surprised by counter-intuitive interactions with underlying hardware resources. We’ll dive deep on a few of these surprises, and try to distill lessons for other dynamic language runtimes.

Photo of Joel Pobar

Joel Pobar


Joel Pobar is a compiler and languages nerd from the sunny Gold Coast Australia. He currently works at Facebook as an Engineering Manager working on the HipHop PHP Virtual Machine ( which drives and scales Previously, he did time at an Investment Bank, and prior to that, worked on the .NET CLR team.


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