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Composer Manager provides a
gateway to the larger PHP community by enabling Backdrop modules to more easily
use best-in-breed libraries that are managed by

There are many challenges when using Composer with
Backdrop, so the primary goal of this module is to work around them by wrapping
Composer with common Backdrop workflows so that module developers and site
builders can use the thousands of standards-compliant, platform agnostic PHP
with as little friction as


Usage For Site Builders

Maintaining Dependencies

As modules are enabled and disabled, Composer Manager gathers their requirements
and generates a consolidated composer.json file in the "Composer File
Directory" as configured in Composer Manager's settings page. There are two ways
to install and update the contributed modules' dependencies:

Automatically With Drush (Recommended)

Using drush en and drush dis to enable and disable modules respectively will
automatically generate the consolidated composer.json file and run the
appropriate Composer commands to install and update the required dependencies.

This technique introduces the least amount of friction with existing workflows
and is strongly recommended.

The following Drush commands are also available:

  • drush composer-json-rebuild: Force a rebuild of the consolidated
    composer.json file
  • drush composer-manager [COMMAND] [OPTIONS]: Pass through commands to
    Composer, refer to the cli tool's documentation
    for available commands and options.

Manually With Composer

If you do not wish to use Drush, you must manually use Composer's command line
tool to install and update dependencies whenever modules are enabled or
disabled. The following steps illustrate the workflow to maintain the
dependencies required by contributed module:

  • Visit admin/modules and enable / disable the modules that have dependencies
  • Change into the the "Composer File Directory" as configured in Composer
    Manager's settings page which is where the consolidated composer.json file
    was generated
  • If necessary, download and install
    the Composer tool
  • Run php composer.phar install --no-dev on the command line, replace
    install with update when updating dependencies

Refer to Composer's documentaton for more
details on how Composer works.

Configuring Composer Manager

Visit admin/config/system/composer-manager/settings as a user with the
administer site configuration permission to configure Composer Manager.

Best Practices

Unfortunately there is arguably no 80% use case that guides sane defaults. Site
builders will likely have to configure Composer Manager according to their
environment, so this section outlines best practices and techniques to help
guide a sustainable, reliable installation.

Recommended Settings

It is recommended to maintain a project structure where the composer files and
vendor/ directory exist alongside the document root. This can be achieved by
modifying the following options in Composer Manager's settings page.

  • Vendor Directory: ../vendor
  • Composer File Directory: ../

You can also set the options in settings.php by adding the following variables:

$config['composer_manager.settings']['vendor_dir'] = '../vendor';
$config['composer_manager.settings']['file_dir'] = '../';

NOTE: The recommended settings are not the defaults because we cannot assume
that this structure is viable for all use cases. Furthermore, the "Composer File
Directory" is set to a path we know is writable by the web server so the
automatic building of composer.json works out of the box.


It is recommended that each multisite installation has its own library space
since the dependencies are tied to which modules are enabled or disabled and
can differ between sites. Add the following snippet to settings.php to group
the libraries by site in a directory outside of the document root:

// Capture the site dir, e.g. "default", "example.localhost", etc.
$site_dir = basename(__DIR__);
$config['composer_manager.settings']['vendor_dir'] = '../lib/' . $site_dir . '/vendor';
$config['composer_manager.settings']['file_dir'] = '../lib/' . $site_dir;

NOTE: The sites/*/ directories may seem like an obvious location for the
libraries, however Backdrop removes write permissions to these directories on
every page load which can cause frustration.

Production Environments

Dependencies should be managed in development environments and not in production.
Therefore it is recommended to disable the checkboxes that automatically build
the composer.json file and run Composer commands when enabling or disabling
modules on production environments.

Assuming that you can detect whether the site is in production mode via an
environment variable, adding the following snippet to settings.php will
disable the options where appropriate:

// Modify the logic according to your environment.
if (getenv('APP_ENV') == 'prod') {
  $config['composer_manager.settings']['autobuild_file'] = 0;
  $config['composer_manager.settings']['autobuild_packages'] = 0;

Usage For Module Maintainers

Module maintainers can use Composer Manager to maintain their dependencies by
creating a composer.json file in the module's root directory and adding the
appropriate requirements. Refer to Composer's documentation
for details on adding requirements.

It is recommended to use version ranges
and tilde operators
wherever possible to mitigate dependency conflicts.

You can also implement hook_composer_json_alter(&$json) to modify the data
used to build the consolidated composer.json file before it is written.

Maintaining A Soft Dependency On Composer Manager


Accessing The ClassLoader Object

Once the autoloader is registered, you can retrieve the ClassLoader object by
calling \ComposerAutoloaderInitComposerManager::getLoader(). The following
example uses this technique with Doctrine's Annotations library which requires
access to the loader object.

use Doctrine\Common\Annotations\AnnotationRegistry;

$loader = \ComposerAutoloaderInitComposerManager::getLoader();
AnnotationRegistry::registerLoader(array($loader, 'loadClass'));

Relying on composer manager in .install

Composer manager will automatically handle the autoloader in hook_init(), so
modules generally don't have to worry about triggering the autoloader. However
there are occasions where hook_init() isn't invoked such as during install and
update.php. If you rely on the autoloader in a .install file, you have to make
sure the autoloader is triggered by running
composer_manager_register_autoloader() at the beginning of your update
function or your hook_install() implementation.

Why can't you just ... ?

The problems that Composer Manager solves tend to be more complex than they
first appear. This section addresses some of the common questions that are asked
as to why Composer Manager works the way it does.

Why can't you just run "composer install" in each module's root directory?

If a module contains a composer.json file, running composer install in its
root directory will download all requirements and dependencies to vendor/
directories with their own autoloaders. Relying on this technique poses multiple

  • Duplicate library code when modules have the same dependencies
  • Unexpected classes being sourced depending on which autoloader is registered
  • Potential version conflicts that aren't detected since each installation is
    run in isolation

To highlight the challenges, let's say module_a requires
"guzzle/http": "3.7.*" and module_b requires "guzzle/service": ">=3.7.0".
At the time of this post, running composer install in each module's directory
will result in version 3.7.4 of guzzle/http being installed in module_a's
vendor/ directory and version 3.8.1 of guzzle/service being installed in
module_b's vendor/ directory.

Because guzzle/service depends on guzzle/http, you now have duplicate
installs of guzzle/http. Furthermore, each installation uses different
versions of the guzzle/http component (3.7.4 for module_a and 3.8.1 for
module_b). If module_a's autoloader is registered first then you have a
situation where version 3.8.1 of \Guzzle\Service\Client extends version 3.7.4
of \Guzzle\Http\Client.

Composer Manager's Solution

Composer Manager finds all composer.json files in each enabled module's root
directory and attempts to gracefully merge them into a consolidated
composer.json file. This results in a single vendor directory shared across
all modules which prevents code duplication and version mismatches. For the use
case above, Composer will resolve both guzzle/http and guzzle/service to
version 3.7.4 which is a more consistent, reliable environment.

Challenges With Composer Manager

The challenge of Composer Manager's technique is when multiple modules require
different version of the same package, e.g. "guzzle/http": "3.7.*" and
"guzzle/http": "3.8.*". Composer Manager will use the version defined in the
composer.json file that is associated with the module with the heaviest weight.
Composer Manager will also flag the potential version conflict in the UI so the
site builder is aware of the inconsistency.

Why can't you just manually maintain a composer.json file?

Manually maintaining a composer.json file provides a single library space that
all modules can share, however relying on this technique poses multiple

  • Site builder responsible for updating file when modules are enabled or updated
  • Dependencies are decoupled from the module's codebase
  • Multiple files must be maintained for each multisite installation

Composer Manager's Solution

Composer Manager automatically generates the composer.json file when modules
are enabled and disabled, and there is an option in the UI with a corresponding
Drush command that can rebuild the consolidated composer.json file on demand.
Furthermore, using a Drush based workflow will automatically run the appropriate
composer commands whenever modules are enabled or disabled, so the need to run
Composer commands outside of normal workflows is reduced to module updates.

Challenges With Composer Manager

There are multiple challenges posed by Composer Manager's technique:

  • Web server needs write access to the composer file directory
  • Sane multisite configuration requires environment-specific settings.php
  • Must implement hook_composer_json_alter() in a module to modify

Composer Manager's Solution

Refer to the Why can't you just manually maintain a composer.json file?

Challenges With Composer Manager

Refer to the Why can't you just manually maintain a composer.json file?

Current Maintainers



This project is GPL v2 software. See the LICENSE.txt file in this directory for
complete text.