How to get the root package path using composer

I'm developing a PHP component called php-app-config using composer. This component, once required by another project, and installed using composer install, should look for config files inside the config folder of the root package, something like root_package/config/config.yml.

The ./config/config.yml should exists only in the root package and not inside the component imported by the "require:" in composer.json, as below:

▾ root-package/
  ▸ bin/
  ▸ build/
  ▾ config/
    ▸ locales/
      config.yml
  ▸ src/
  ▸ tests/
  ▾ vendor/
    ▸ composer/
    ▸ phpdocumentor/
    ▸ phpspec/
    ▸ phpunit/
    ▾ robotdance/
      ▾ php-app-config/
        ▾ src/                                                                                                                                                                                               
      Config.php -> how to get the root "config/config.yml" path from here?
        ▸ tests/
      composer.json
      composer.lock
      phpunit.xml
      README.md

The root package can be a web app or command line utility. Is there any way to get the root package path using composer? If not, what is the better way?

Using ReflectionClass:

$reflection = new \ReflectionClass(\Composer\Autoload\ClassLoader::class);
$vendorDir = dirname(dirname($reflection->getFileName()));

You can use composer's very own \Composer\Factory::getComposerFile(); to get to the project root directory:

$projectRootPath = dirname(\Composer\Factory::getComposerFile());

And with your case, you can access your root-package/config/config.yml by:

$configYmlPath = $projectRootPath . '/config/config.yml'

Don't forget to add composer to your dependencies for the \Composer\Factory::class to be available:

$ composer require composer/composer

• I would suggest "anchoring" your application (web or cli) by defining the root path as a constant.

  When you have for instance a root-package/src/application.php file, it should know where it lives, something like define('APP_ROOT_FOLDER', dirname(__DIR__)); could help. Once the constant is declared, it's available for dependencies, too.

  So, in /php-app-config/Config.php you would simply use the constant:

  $config = APP_ROOT_FOLDER . '/config/config.yml';

  (Or define a APP_CONFIG_ROOT_FOLDER constant which points directly to the config folder of the application.)

• You could also try go some folder levels up from the dependency.

  In php-app-config/Config.php you would use __DIR__, which is root-package/vendor/robotdance/php-app-config/src. Now, you would need to go 4 levels up to reach root-package/.

  $config = __DIR__.'/../../../../config/config.yml';

  This will not work out, when your application gets packaged as a PHAR.

Is there any way to get the root package path using Composer?

If you have the Composer object, you can get the path of the vendor directory from the Config object:

$vendorPath = $composer->getConfig()->get('vendor-dir');

then, go one folder up $config = dirname($vendorPath) . '/config/config.yml';