Hack extends the PHP language with a gradual typing system. It allows large PHP codebases to introduce powerful, flexible type assurances incrementally, one file or even one function declaration at a time. Unlike PHP 5 and 7’s long-standing typehint mechanisms, Hack checks type invariants soundly ahead of time, before running the code. Slack has recently begun migrating its large PHP codebase to Hacklang, with a goal of reducing defect density, and increasing the confidence and velocity of changes. I’ll introduce the Hack language, narrate Slack’s experience in migrating to it, and offer some lessons learned for others contemplating the switch.


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Paul McKibben at 15:36 on 24 May 2017

Good introduction to Hack

John Hackett at 16:40 on 24 May 2017

Seemed to kind of ramble through the info, so not much stuck with me....

Yar at 17:20 on 24 May 2017

Stick to the slides. Presentation me want to to go back to IRC.

Ed Barnard at 05:48 on 25 May 2017

This talk was useful to me in seeing where hack fits into the PHP ecosystem. We had good concrete examples showing the concepts. This might have been less clear for people who aren't familiar with "struct" concepts for other languages, but it was easy enough to see from the examples.

I love how Adam provided the arguments why and how Slack decided to improve their codebase. Good talk, great examples and wonderful slides. Well done!

Not sure how relevant the talk was to this conference

Mark Knapik at 10:28 on 29 May 2017


Was quite different from most talks in that it was focused on using Hack and their experiences migrating to it. I did learn a few things about Hack and some benefits, but with advancements made in PHP 7, having good unit tests, and recent discussions about future features in PHP it is hard to find good reasons to migrate. Overall a good keynote but not great.

SH at 17:29 on 30 May 2017

It wasn't too relevant for what I am doing. But that's ok, it was still very interesting to hear what others are doing and hear their stories of work and accomplishment!

Sandy Smith at 15:46 on 6 Jun 2017

Excellent coverage of Hack, and a very good case study of dealing with codebases at scale.