Composer is a package management tool for PHP that lets you install and upgrade SilverStripe and its modules. Although installing Composer is one extra step, it will give you much more flexibility than just downloading the file from silverstripe.org. This is our recommended way of downloading SilverStripe and managing your code.
Before installing Composer you should ensure your system has the version control system, [Git installed](http://git-scm.com/book/en/v2/Getting-Started-Installing-Git). Composer uses Git to check out the code dependancies you need to run your SilverStripe CMS website from the code repositories maintained on GitHub.
It is also possible to keep `composer.phar` out of your path, for example, to put it in your project root. Every command would then start with `php composer.phar` instead of `composer`. This is handy if need to keep your installation isolated from the rest of your computer's set-up, but we recommend putting composer into the path for most people.
For those that use WAMP as a development environment, [detailed information is available on installing using Composer.](/getting_started/installation/windows)
Composer isn't only used to download SilverStripe CMS, it is also used to manage all SilverStripe modules. Installing a module can be done with the following command:
This will install the forum module in the latest compatible version. If you know the specific version you want to install already (such as `^0.8`), you can add it after the package name. For more information, read the [Composer documentation](http://getcomposer.org/doc/01-basic-usage.md#the-require-key):
This will return a list of package names of the forum `vendor/package`. If you prefer, you can search for packages on [packagist.org](https://packagist.org/search/?q=silverstripe).
**Version constraints:** `master` is not a legal version string - it's a branch name. These are different things. The version string that would get you the branch is `dev-master`. The version string that would get you a numeric branch is a little different. The version string for the `4` branch is `4.x-dev`.
Except for the control code of the Voyager space probe, every piece of code in the universe gets updated from time to time. SilverStripe modules are no exception.
Updates to the required modules will be installed, and the `composer.lock` file will get updated with the specific commits and version constraints for each of them.
When deploying projects with composer, you could just push the code and run `composer update`. This, however, is risky. In particular, if you were referencing development dependencies and a change was made between your testing and your deployment to production, you would end up deploying untested code. Not cool!
The `composer.lock` file helps with this. It references the specific commits that have been checked out, rather than the version string. You can run `composer install` to install dependencies from this rather than `composer.json`.
* Run `composer install --no-dev -o` on your production version. In this command, the `--no-dev` command tells Composer not to install your development-only dependencies, and `-o` is an alias for `--optimise-autoloader`, which will convert your PSR-0 and PSR-4 autoloader definitions into a classmap to improve the speed of the autoloader.
Modules and themes managed by composer should not be committed with your projects source code. For more details read [Should I commit the dependencies in my vendor directory?](https://getcomposer.org/doc/faqs/should-i-commit-the-dependencies-in-my-vendor-directory.md).
Since SilverStripe modules are installed into their own folder, you have to manage your [.gitignore](http://git-scm.com/docs/gitignore) to ensure they are ignored from your repository.
In large projects it can get difficult to manage your [.gitignore](http://git-scm.com/docs/gitignore) and ensure it contains all composer managed modules and themes.
You can automate this with the [SSAutoGitIgnore](https://github.com/guru-digital/SSAutoGitIgnore/) package.
This package will maintain your [.gitignore](http://git-scm.com/docs/gitignore) and ensure it is kept up to date with your composer managed modules without affecting custom ignores. Once installed and setup, it will automatically run every time you install, remove or update modules using composer.
### Installing and enabling the SSAutoGitIgnore package
Include the package in your project by running this command
This will instruct composer to run SSAutoGitIgnore after every update. SSAutoGitIgnore will then ensure composer managed models and themes are correctly added to your [.gitignore](http://git-scm.com/docs/gitignore).
For more information about SSAutoGitIgnore, see the [SSAutoGitIgnore home page](https://github.com/guru-digital/SSAutoGitIgnore/).
For more information about post-updated-cmd and scripts, read the ["Scripts" chapter of the Composer documentation](https://getcomposer.org/doc/articles/scripts.md).
Full example of composer.json with the SSAutoGitIgnore installed and enabled
The process will take a bit longer, since all modules are checked out as full git repositories which you can work on. The command checks out from the 4.0 release line. To check out from master instead,
replace `4.0.x-dev` with `dev-master` (more info on [composer version naming](http://getcomposer.org/doc/02-libraries.md#specifying-the-version)).
To remove dependencies, or if you prefer seeing all your dependencies in a text file, you can edit the `composer.json` file. It will appear in your project root, and by default, it will look something like this:
```json
{
"name": "silverstripe/installer",
"description": "The SilverStripe Framework Installer",
To add modules, you should add more entries into the `"require"` section. For example, we might add the blog and forum modules. Be careful with the commas at the end of the lines!
Composer will by default download the latest stable version of silverstripe/installer.
The `composer.json` file that comes with silverstripe/installer may also explicitly state it requires the stable version of cms and framework - this is to ensure that when developers are getting started, running `composer update` won't upgrade their project to an unstable version
However it is relatively easy to tell composer to use development versions. Not only
is this required if you want to contribute back to the SilverStripe project, it also allows you to get fixes and API changes early.
This is a two step process. First you get composer to start a project based on
* You may have your own fork of a module, either specific to a project, or because you are working on a pull request
* You may have a module that hasn't been released to the public.
There are many ways that you can address this, but this is one that we recommend, because it minimises the changes you would need to make to switch to an official version in the future.
* **Ensure that all of your fork repositories have correct composer.json files.** Set up the project forks as you would a distributed package. If you have cloned a repository that already has a composer.json file, then there's nothing you need to do, but if not, you will need to create one yourself.
* **List all your fork repositories in your project's composer.json files.** You do this in a `repositories` section. Set the `type` to `vcs`, and `url` to the URL of the repository. The result will look something like this:
* **Install the module as you would normally.** Use the regular composer function - there are no special flags to use a fork. Your fork will be used in place of the package version.
Composer will scan all of the repositories you list, collect meta-data about the packages within them, and use them in favour of the packages listed on packagist. To switch back to using the mainline version of the package, just remove the `repositories` section from `composer.json` and run `composer update`.
Generally, you should keep using the same pattern of branch names as the main repositories does. If your version is a fork of 4.0, then call the branch `4.0`, not `4.0-myproj` or `myproj`. Otherwise, the dependency resolution gets confused.
Sometimes, however, this isn't feasible. For example, you might have a number of project forks stored in a single repository, such as your personal GitHub fork of a project. Or you might be testing/developing a feature branch. Or it might just be confusing to other team members to call the branch of your modified version `4.0`.
In this case, you need to use Composer's aliasing feature to specify how you want the project branch to be treated, when it comes to dependency resolution.
What this means is that when the `myproj` branch is checked out into a project, this will satisfy any dependencies that `4.0.x-dev` would meet. So, if another module has `"silverstripe/framework": "^4.0.0"` in its dependency list, it won't get a conflict.
Both the version and the alias are specified as Composer versions, not branch names. For the relationship between branch/tag names and Composer versions, read [the relevant Composer documentation](http://getcomposer.org/doc/02-libraries.md#specifying-the-version).
This is not the only way to set things up in Composer. For more information on this topic, read the ["Aliases" chapter of the Composer documentation](http://getcomposer.org/doc/articles/aliases.md).
create a `composer.json`, and either commit it or send a pull request to the module author.
Look at existing modules like the ["blog" module](https://github.com/silverstripe/silverstripe-blog/blob/master/composer.json) for good examples on what this file should contain.
Follow the packagist.org advice on choosing a [unique name and vendor prefix](https://packagist.org/about). Please don't use the `silverstripe/<modulename>` vendor prefix, since that's reserved
for modules produced by SilverStripe Ltd. In order to declare that your module is
in fact a SilverStripe module, use the "silverstripe" tag in the composer.json file,
