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v2.0.8 2019-08-28 15:08 UTC


A Composer plugin for autoloading classes, enums, functions, typedefs, and constants on HHVM.


Do I need to use Hack?

No, PHP is fine - but HHVM is required because:

  • PHP does not support autoloading anything other than classes
  • this project and the parser are written in Hack

Can I autoload functions and constants if I'm not writing Hack?

Yes :)

Why does this project use Composer's autoloader?

It can't depend on itself :)


  1. Add an hh_autoload.json file (see section below) and optionally remove your configuration from composer.json
  2. composer require hhvm/hhvm-autoload
  3. Replace any references to vendor/autoload.php with vendor/hh_autoload.hh
  4. If you are using PHPUnit, you will need to add vendor/hh_autoload.hh to your bootstrap.php, or to phpunit.xml as a bootstrap file if you don't already have one. This is because PHPUnit automatically loads vendor/autoload.php, but is not aware of vendor/hh_autoload.hh
  5. To re-generate the map, run vendor/bin/hh-autoload, composer dump-autoload, or any other command that generates the map

Configuration (hh_autoload.json)

A minimal configuration file is:

  "roots": [ "src/" ]

This will look for autoloadable definitions in src/, and also look in vendor/. It will pay attention to the autoload sections of composer.json inside the vendor/ directory.

The following settings are optional:

  • "extraFiles": ["file1.php"] - files that should not be autoloaded, but should be require()ed by vendor/hh_autoload.hh. This should be needed much less frequently than under Composer
  • "includeVendor": false - do not include vendor/ definitions in vendor/hh_autoload.hh
  • "autoloadFilesBehavior": "scan"|"exec" - whether autoload files from vendor should be scanned for definitions, or executed by vendor/hh_autoload.hh - scan is the default, and generally favorable, but exec is needed if you have dependencies that need code to be executed on startup. scan is sufficient if your dependencies just use files because they need to define things that aren't classes, which is usually the case.
  • "devRoots": [ "path/", ...] - additional roots to only include in dev mode, not when installed as a dependency.
  • "relativeAutoloadRoot": false - do not use a path relative to __DIR__ for autoloading. Instead, use the path to the folder containing hh_autoload.json when building the autoload map.
  • "failureHandler:" classname<Facebook\AutoloadMap\FailureHandler> - use the specified class to handle definitions that aren't the Map. Your handler will not be invoked for functions or constants that aren't in the autoload map and have the same name as a definition in the global namespace. Defaults to none.
  • "devFailureHandler": classname<Facebook\AutoloadMap\FailureHandler> - use a different handler for development environments. Defaults to the same value as failureHandler.

Use In Development (Failure Handlers)

When you add, remove, or move definitions, there are several options available:

  • run composer dump-autoload to regenerate the map
  • run vendor/bin/hh-autoload to regenerate the map faster
  • specify devFailureHandler as Facebook\AutoloadMap\HHClientFallbackHandler
  • specify a custom subclass of Facebook\AutoloadMap\FailureHandler
  • use a filesystem monitor such as watchman to invoke one of the above commands when necessary

Facebook\AutoloadMap\HHClientFallbackHandler is probably the most convenient for Hack development.

For performance reasons, failure handler methods will not be invoked for namespaced functions or constants that have the same name as one in the global namespace. You will need to re-generate the map if you make changes to functions or constants that are affected by this restriction.


If you are working in Hack, this handler will remove the need to manually rebuild the map in almost all circumstances.

It asks hh_client for definitions that aren't in the map, and has the following additional behaviors:

  • it is disabled if the CI, CONTINUOUS_INTEGRATION, or TRAVIS environment variables are set to a Truthy value; this is because it is not a recommended approach for production environments, and you probably want your automated testing environment to reflect production
  • results are cached in both APC and a file in vendor/, if vendor/ is writable

You can override these behaviors in a subclass.

As it is based on hh_client, it is unable to handle PHP definitions - however, if you're using composer, changes to your PHP dependencies will automatically trigger a map rebuild.

Custom Handlers

Information you may need is available from:

  • Facebook\AutoloadMap\Generated\build_id(): this is unique ID regenerated every time the map is rebuilt; it includes the date, time, and a long random hex string. If your failure handler has a cache, it most likely should be invalidated when this changes, for example, by including it in the cache key.
  • Facebook\AutoloadMap\Generated\map(): the autoload map
  • Facebook\AutoloadMap\Generated\root(): the directory containing the project root, i.e. the parent directory of vendor/

How It Works

  • A parser (FactParse or DefinitionFinder) provides a list of all PHP and Hack definitions in the specified locations
  • This is used to generate something similar to a classmap, except including other kinds of definitions
  • The map is provided to HHVM with HH\autoload_set_paths()

The Composer plugin API allows it to re-generate the vendor/hh_autoload.hh file automatically whenever Composer itself regenerates vendor/autoload.php


We welcome GitHub issues and pull requests - please see CONTRIBUTING.md for details.


hhvm-autoload is MIT-licensed.