Composer

Flarum uses a program called Composer to manage its dependencies and extensions. You'll need to use composer if you want to:

• Install or update Flarum through the command line
• Install, update, or remove Flarum extensions through the command line

This guide is provided as a brief explanation of Composer. We highly recommend consulting the official documentation for more information.

#What is Composer?

Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you. — Composer Introduction

Each Flarum installation consists primarily of Flarum core and a set of extensions. Each of these has its own dependencies and releases.

Back in the day, forum frameworks would manage extensions by having users upload zip files with the extension code. That seems simple enough, but issues quickly become evident:

• Uploading random zip files from the internet tends to be a bad idea. Requiring that extensions be downloaded from a central source like Packagist makes it somewhat more tedious to spam malicious code, and ensures that source code is available on GitHub for free/public extensions.
• Let's say Extension A requires v4 of some library, and Extension B requires v5 of that same library. With a zip-based solution, either one of the two dependencies could override the other, causing all sorts of inconsistent problems. Or both would attempt to run at once, which would cause PHP to crash (you can't declare the same class twice).
• Zip files can cause a lot of headache if trying to automate deployments, run automated tests, or scale to multiple server nodes.
• There is no good way to ensure conflicting extension versions can't be installed, or that system PHP version and extension requirements are met.
• Sure, we can upgrade extensions by replacing the zip file. But what about upgrading Flarum core? And how can we ensure that extensions can declare which versions of core they're compatible with?

Composer takes care of all these issues, and more!

#Flarum and Composer

When you go to install Flarum, you're actually doing 2 things:

1. Downloading a boilerplate "skeleton" for Flarum. This includes an index.php file that handles web requests, a flarum file that provides a CLI, and a bunch of web server config and folder setup. This is taken from the flarum/flarum github repository, and doesn't actually contain any of the code necessary for Flarum to run.
2. Installing composer packages necessary for Flarum, namely Flarum core, and several bundled extensions. These are called by the index.php and flarum files from step 1, and are the implementation of Flarum. These are specified in a composer.json file included in the skeleton.

When you want to update Flarum or add/update/remove extensions, you'll do so by running composer commands. Each command is different, but all commands follow the same general process:

1. Update the composer.json file to add/remove/update the package.
2. Do a bunch of math to get the latest compatible versions of everything if possible, or figure out why the requested arrangement is impossible.
3. If everything works, download new versions of everything that needs to be updated. If not, revert the composer.json changes

When running composer.json commands, make sure to pay attention to the output. If there's an error, it'll probably tell you if it's because of extension incompatibilities, an unsupported PHP version, missing PHP extensions, or something else.

#The composer.json File

As mentioned above, the entire composer configuration for your Flarum site is contained inside the composer.json file. You can consult the composer documentation for a specific schema, but for now, let's go over an annotated composer.json from flarum/flarum:

{
    // This following section is mostly just metadata about the package.
    // For forum admins, this doesn't really matter.
    "name": "flarum/flarum",
    "description": "Delightfully simple forum software.",
    "type": "project",
    "keywords": [
        "forum",
        "discussion"
    ],
    "homepage": "https://flarum.org/",
    "license": "MIT",
    "authors": [
        {
            "name": "Flarum",
            "email": "[email protected]",
            "homepage": "https://flarum.org/team"
        }
    ],
    "support": {
        "issues": "https://github.com/flarum/core/issues",
        "source": "https://github.com/flarum/flarum",
        "docs": "https://flarum.org/docs/"
    },
    // End of metadata

    // This next section is the one we care about the most.
    // It's a list of packages we want, and the versions for each.
    // We'll discuss this shortly.
    "require": {
        "flarum/core": "^1.0",
        "flarum/approval": "*",
        "flarum/bbcode": "*",
        "flarum/emoji": "*",
        "flarum/lang-english": "*",
        "flarum/flags": "*",
        "flarum/likes": "*",
        "flarum/lock": "*",
        "flarum/markdown": "*",
        "flarum/mentions": "*",
        "flarum/nicknames": "*",
        "flarum/pusher": "*",
        "flarum/statistics": "*",
        "flarum/sticky": "*",
        "flarum/subscriptions": "*",
        "flarum/suspend": "*",
        "flarum/tags": "*"
    },

    // Various composer config. The ones here are sensible defaults.
    // See https://getcomposer.org/doc/06-config.md for a list of options.
    "config": {
        "preferred-install": "dist",
        "sort-packages": true
    },

    // If composer can find a stable (not dev, alpha, or beta) version
    // of a package, it should use that. Generally speaking, production
    // sites shouldn't run beta software unless you know what you're doing.
    "prefer-stable": true
}

Let's focus on that require section. Each entry is the name of a composer package, and a version string. To read more about version strings, see the relevant composer documentation.

For Flarum projects, there's several types of entries you'll see in the require section of your root install's flarum/core:

• You MUST have a flarum/core entry. This should have an explicit version string corresponding to the major release you want to install. For Flarum 1.x versions, this would be ^1.0.
• You should have an entry for each extension you've installed. Some bundled extensions are included by default (e.g. flarum/tags, flarum/suspend, etc), others you'll add via composer commands. Unless you have a reason to do otherwise (e.g. you're testing a beta version of a package), we recommend using an asterisk as the version string for extensions (*). This means "install the latest version compatible with my flarum/core".
• Some extensions / features might require PHP packages that aren't Flarum extensions. For example, you need the guzzle library to use the Mailgun mail driver. In these cases, the instructions for the extension/feature in question should explain which version string to use.

#How to install Composer?

As with any other software, Composer must first be installed on the server where Flarum is running. There are several options depending on the type of web hosting you have.

#Dedicated Web Server

In this case you can install composer as recommended in the Composer guide

#Managed / Shared hosting

If Composer is not preinstalled (you can check this by running composer --version), you can use a manual installation. Just upload the composer.phar to your folder and run /path/to/your/php7 composer.phar COMMAND for any command documented as composer COMMAND.

#How do I use Composer?

You'll need to use Composer over the Command-line interface (CLI). Be sure you can access your server over Secure Shell (SSH).

Once you have Composer installed, you should be able to run Composer commands in your SSH terminal via composer COMMAND.