silverstripe-framework/docs/en/02_Developer_Guides/05_Extending/00_Modules.md

title: Modules
summary: Extend core functionality with modules.

# Modules

SilverStripe is designed to be a modular application system - even the CMS is simply a module that plugs into the core
framework.

A module is a collection of classes, templates, and other resources that is loaded into a top-level directory such as
the `framework`, `cms` or `mysite` folders. The only thing that identifies a folder as a SilverStripe module is the
existence of a `_config` directory or `_config.php` at the top level of the directory.

```
mysite/
|
+-- _config/
+-- src/
+-- ..
|
my_custom_module/
|
+-- _config/
+-- ...
```

SilverStripe will automatically include any PHP classes and templates from within your module when you next flush your
cache.

<div class="info" markdown="1">
In a default SilverStripe installation, even resources in `framework` and `mysite` are treated in exactly the same as
every other module. Order of priority is usually alphabetical unless stated.
</div>

Creating a module is a good way to re-use abstract code and templates across multiple projects. SilverStripe already
has certain modules included, for example the `cms` module and core functionality such as commenting and spam protection
are also abstracted into modules allowing developers the freedom to choose what they want.


## Finding Modules

* [Official module list on silverstripe.org](http://addons.silverstripe.org/)
* [Packagist.org "silverstripe" tag](https://packagist.org/search/?tags=silverstripe)
* [GitHub.com "silverstripe" search](https://github.com/search?q=silverstripe)

## Installation

Modules should exist in the root folder of your SilverStripe installation.

<div class="info" markdown="1">
The root directory is the one containing the *framework* and *mysite* subdirectories. If your site is installed under
`/Users/sam.minnee/Sites/website/` your modules will go in the `/Users/sam.minnee/Sites/website/` directory.
</div>

<div class="notice" markdown="1">
After you add or remove modules, make sure you rebuild the database, class and configuration manifests by going to http://yoursite.com/dev/build?flush=1
</div>

### From Composer

Our preferred way to manage module dependencies is through the [Composer](http://getcomposer.org) package manager. It
enables you to install modules from specific versions, checking for compatibilities between modules and even allowing
to track development branches of them. To install modules using this method, you will first need to setup SilverStripe
with [Composer](../../getting_started/composer).

Each module has a unique identifier, consisting of a vendor prefix and name. For example, the "blog" module has the
identifier `silverstripe/blog` as it is published by *silverstripe*. To install, use the following command executed in
the root folder:

```bash
composer require silverstripe/blog *@stable
```

This will fetch the latest compatible stable version of the module. To install a specific version of the module give the
tag name.

```bash
composer require silverstripe/blog 1.1.0
```

<div class="info" markdown="1">
For more information on using Composer version constraints, please [see here](https://getcomposer.org/doc/articles/versions.md). To lock down to a specific version, branch or commit, read up on
[Composer "lock" files](http://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file).
</div>

## From an Archive Download

<div class="alert" markdown="1">
Some modules might not work at all with this approach since they rely on the
Composer [autoloader](http://getcomposer.org/doc/01-basic-usage.md#autoloading), additional modules or post-install
hooks, so we recommend using Composer.
</div>

Alternatively, you can download the archive file from the [modules page](http://www.silverstripe.org/modules) and
extract it to the root folder mentioned above.

<div class="notice" markdown="1">
The main folder extracted from the archive might contain the version number or additional "container" folders above the
actual module codebase. You need to make sure the folder name is the correct name of the module (e.g. "blog/" rather
than "silverstripe-blog/"). This folder should contain a `_config/` directory. While the module might register and
operate in other structures, paths to static files such as CSS or JavaScript won't work.
</div>

## Publishing your own SilverStripe module

See the [How to Publish a SilverStripe Module](how_tos/publish_a_module) for details on how to publish your SilverStripe
modules with the community

## Module Standard

The SilverStripe module standard defines a set of conventions that high-quality SilverStripe modules should follow. It’s a bit like PSR for SilverStripe CMS. Suggested improvements can be raised as pull requests.

### Coding Guidelines

 * Declaration of level of support is provided for each module (either via README.md or composer) including the following:
   * Level of support provided.
   * Supporting user(s) and/or organisation(s).
 * Complies to a well defined module directory structure and coding standards:
   * `templates/` (for `.ss` templates)
   * `src/` (for `.php` files)
   * `tests/` (for `*Test.php` test files), and;
   * `_config/` (for `.yml` config files)
 * The module is a Composer package.
 * All Composer dependencies are bound to a single major release (e.g. `^4.0` not `>=4` or `*`).
 * There is a level of test coverage.
 * A clear public API documented in the docblock tags.
 * Code follows [PSR-1](http://www.php-fig.org/psr/psr-1/) and [PSR-2](http://www.php-fig.org/psr/psr-2/) style guidelines.
 * `.gitattributes` will be used to exclude non-essential files from the distribution. At a minimum tests, docs, and IDE/dev-tool config should be excluded.
 * Add a [PSR-4 compatible autoload reference](https://getcomposer.org/doc/04-schema.md#psr-4) for your module.

### Documentation Guidelines

Documentation will use the following format:

 * README.md provides:
   * Links or badges to CI and code quality tools.
   * A short summary of the module, end-user.
   * Installation instructions.
   * Testing/development instructions and a link to contributing instructions.
   * How to report security vulnerabilities. Note that PSR-9 / PSR-10 may be recommended once released.
   * Security, license, links to more detailed docs.
 * CONTRIBUTING.md explaining terms of contribution.
 * A changelog: CHANGELOG.md (may link to other more detailed docs or GitHub releases if you want). You could [use a changelog generator](https://github.com/skywinder/Github-Changelog-Generator) to help create this.
 * Has a licence (`LICENSE` file) - for SilverStripe supported this needs to be BSD.
 * Detailed documentation in `/docs/en` as a nested set of GitHub-compatible Markdown files.
 * It is suggested to use a documentation page named `userguide.md` in `docs/en/` that includes documentation of module features that have CMS user functionality (if applicable). For modules with large userguides, this should be in a directory named `userguide` with an `index.md` linking to any other userguide pages.
 * Links and image references are relative, and are able to be followed in viewers such as GitHub.
 * Markdown may include non-visible comments or meta-data.

Documentation will cover:

 * Installation
 * Configuration
 * Usage guides for key features; screenshots are recommended.
 * A committers guide, covering pull request merging and release guidelines.

## Related

* [How to Publish a SilverStripe Module](how_tos/publish_a_module)