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Documentation for those that use HHVM and write Hack and PHP code for HHVM.
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HHVM and Hack User Documentation Build Status

This is the repo for the HHVM and Hack user documentation. Contributions and feedback are welcome.

If you see anything egregious, you can file an issue or ping us at #hhvm-dev on Freenode IRC or on Facebook


There are three keys areas to this repo:

  • User Documentation: The guides. We realized that finding out how to do simple things like setting up HHVM to more complicated things like using async were more tedious than they should be. The documentation should be a friend, not a nuisance.
  • API Reference: We use our own HHVM code documentation for Hack and HHVM specific API documentation. And for anything PHP specific, we defer to This serves two purposes:
    • The HHVM source code is the source of truth
    • We don't duplicate PHP documentation, and their documentation will serve as the source of truth for PHP-specific documentation
  • Infrastructure: An easier, more modular and scalable way for documentation. Markdown, not docbook, for user-guide content. Easy to follow, Hack-based source code for building the site.


Our strategy to create better documentation begins with a re-thinking of our doc infrastructure.

  • Markdown instead of docbook provides an easier path for documentation source readability and updates.
    • Have extensions to support things like example insertion, etc.
  • Token scan our the HHVM code block documentation (instead of reflection) so that rebuilding HHVM isn't necessary to update the documentation.
  • Ensure the source code that builds the site is as reusable as possible, so that it has the potential to provide reusability to documentation projects beyond Hack and HHVM.

Check out the source code for building the site. bin/build.php is where all the execution begins.

Running A Local Copy

If you just want to quickly run a copy and don't plan on contributing changes:

  1. Install Docker
  2. docker run -p 8080:80 -d hhvm/user-documentation; this will output a container ID
  3. You can then access a local copy of the documentation at http://localhost:8080
  4. To stop the instance, run docker stop ID_FROM_STEP_2_ABOVE. If you don't have a copy of that ID any more, run docker ps and use the container name in the right-most column instead.

Building The Site

If you would like to build the site locally (e.g., to test your content contributions), you will need to install and configure your system to be able to build and run the site locally.

These are the basic step-by-step instructions to get you up and running. It assumes certain packages are installed on your system. Click here for detailed installation information.

  1. Clone this repository
  2. cd path/to/user-documentation
  3. git submodule update --init
  4. hhvm /path/to/composer.phar install # Make sure you have composer downloaded
  5. sudo gem install bundler # to get Ruby bundles
  6. bundle --path vendor-rb/ # install required ruby bundles
  7. hhvm bin/build.php # build the site!

Running The Site From A Checkout

Configure a webserver and HHVM to serve the public/ directory, with all requests that don't match a file being served by index.php. For local development, HHVM's built-in webserver should be sufficient:

$ cd public
$ hhvm -m server -p 8080 -c ../
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