Introduction to Composer

• The package manager for PHP

• Manages dependencies of your project

• Generates optimized autoloaders

• Can fetch packages from diverse, de-centralized sources

• Together with PHP-FIG initiative, has changed the PHP landscape

https://getcomposer.org/

Composer's Role in a PHP Project

• Centralized control over project lifecycle

• Provides separate production and development paths

• Makes projects self-contained

$ git clone mycompany/project
$ cd project
$ composer install

Scripts vs Plugins

• Two mechanisms for enhancing default Composer functionality

• Use same hooks

  ( i.e. "post-install-cmd" <=> ScriptEvents::POST_INSTALL_CMD )

• Overlap in multiple areas

Composer Script

{
  "name": "mycompany/package",
  "require-dev": {
    "phpunit/phpunit": "~6"
  },
  "scripts": {
    "post-update-cmd": "@clearCache",
    "test": [
      "@clearCache",
      "phpunit"
    ],
    "clearCache": "rm -rf cache/*"
  }
}

Composer Plugin

{
  "name": "mycompany/composer-plugin",
  "type": "composer-plugin"
  "require": {
    "composer-plugin-api": "~1"
  },
  "autoload": {
    "psr-4": {
      "MyCompany\\ComposerPlugin\\": "src/"
    }
  },
  "extra": {
    "class": "MyCompany\\ComposerPlugin\\Plugin"
  }
}

<?php namespace MyCompany\ComposerPlugin;

use Composer\EventDispatcher\EventSubscriberInterface;
use Composer\Plugin\PluginInterface;
use Composer\Script\Event;

class Plugin implements PluginInterface,
                        EventSubscriberInterface
{
  // Hook your code up to Composer events.
  public static function getSubscribedEvents()
  {
    return array(
      ScriptEvents::POST_INSTALL_CMD => 'doSomething',
      ScriptEvents::POST_UPDATE_CMD  => 'doSomething',
    );
  }
  // Actually do something when triggered.
  public static function doSomething(Event $event) {}
}

Patching (1/2)

https://github.com/cweagans/composer-patches

Tip: Get patches from GitHub by appending .diff to any commit URL

Patching (2/2)

Namespace Prefixing (1/2)

• Composer can only handle conflicts if it controls the entire project, starting from the root

• In legacy systems like WordPress, individual plugins might want to use Composer, even though the Core does not use it

• Prefixing allows multiple, potentially conflicting versions of a same library to co-exist in a project

https://github.com/coenjacobs/mozart

Namespace Prefixing (2/2)

Keeping Data Up-to-date (1/2)

• Treat external data as a managed dependency

• Changes can be (version-)controlled

• Makes data part of project's deployment flow

• No need to remember manual updates

Example project: https://github.com/brightnucleus/geolite2-country

Keeping Data Up-to-date (2/2)

Commit Hooks (1/3)

• Treated as a development dependency

• Immediately active after a composer install

• Logic can be coded in PHP

• Multiple, prioritisable scripts on same hook

https://github.com/php-composter/php-composter

Commit Hooks (2/3)

{
  "name": "mycompany/custom-hook",
  "type": "php-composter-action"
  "require": {
    "php-composter/php-composter": "*"
  },
  "autoload": {
    "psr-4": {
      "MyCompany\\CustomHook\\": "src/"
    }
  },
  "extra": {
    "php-composter-hooks": {
      "20.pre-commit":
        "MyCompany\\CustomHook\\MyAction::preCommit"
    }
  }
}

<?php namespace MyCompany\CustomHook;

use PHPComposter\PHPComposter\BaseAction;

class MyAction implements BaseAction
{
  /**
   * Example pre-commit action method.
   */
  public function preCommit()
  {
    echo sprintf(
      'Example Pre-Commit Hook %s @ %s' . PHP_EOL,
      $this->hook,
      $this->root,
    );
  }
}

Commit Hooks (3/3)

Automating Boilerplate Code (1/2)

{
  "name": "mycompany/boilerplate",
  "autoload": {
    "psr-4": {
      "Awesome\\Boilerplate\\Scripts\\": "_scripts/"
    }
  },
  "extra": {
    "mycompany-boilerplate": {
      "config-file": "_config/defaults.php",
    }
  },
  "scripts": {
    "post-create-project-cmd": [
      "MyCompany\\Boilerplate\\Scripts\\Setup::run",
      "rm -rf _scripts",
      "composer update --ansi",
      "phpunit --color=always"
    ]
  }
}

Example project: https://github.com/brightnucleus/boilerplate

Embedded Composer (1/2)

• Provides access to all supported sources

• Built-in event dispatching

• Flexible scripting/plugin system still usable

https://developer.wordpress.org/cli/commands/package/

Embedded Composer (2/2)