So how do I use it?

{
    "name": "vgtf/draco_analytics",
    "description": "Provides functionality for inserting analytics data layer into content",
    "type": "drupal-module",
    "require": {
      "phpunit/phpunit": "~4.8"
    }
}

Make a composer.json for your project

Defining Dependencies

Specify version

Semantic versioning highly recommended
Seriously though, you should be using semantic versioning

~1.2 is equivalent to >=1.2 <2.0.0
~1.2.3 is equivalent to >=1.2.3 <1.3.0

^1.2.3 is equivalent to >=1.2.3 <2.0.0

Tilde - last defined digit
Caret - next major version

Using branches

• Not recommended for production
• dev- prefix
  • dev-develop
  • dev-master

"require-dev": {
    "phpunit/phpunit": "^4.0|^5.0"
},

composer install --no-dev

composer install

Run composer install

So how does it work?

composer install

• Builds dependency tree
• Downloads dependencies into vendor directory
• Runs scripts
• Creates composer.lock
• Creates autoloader

*And probably some other stuff
**May or may not actually be in this order

But I don't want my files in the vendor directory!!

"require": {
        "composer/installers": "^1.1.0"
},
"extra": {
    "installer-paths": {
        "docroot/core": ["type:drupal-core"],
        "docroot/modules/contrib/{$name}": ["type:drupal-module"],
        "docroot/modules/custom/{$name}": ["type:drupal-custom-module"],
        "docroot/profiles/contrib/{$name}": ["type:drupal-profile"],
        "docroot/themes/contrib/{$name}": ["type:drupal-theme"],
        "docroot/themes/custom/{$name}": ["type:drupal-custom-theme"]
    }
}

What is composer.lock?

{
    "_readme": [
        "This file locks the dependencies of your project to a known state",
        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
        "This file is @generated automatically"
    ],
    "hash": "07d8a08e6826be43fbd0f20410de8a4e",
    "content-hash": "10cffb250d249788722cb0dcd504b1ff",
    "packages": [
        {
            "name": "alchemy/zippy",
            "version": "0.3.5",
            "source": {
                "type": "git",
                "url": "https://github.com/alchemy-fr/Zippy.git",
                "reference": "92c773f7bbe47fdb30c61dbaea3dcbf4dd13a40a"
            },
            "dist": {
                "type": "zip",
                "url": "https://api.github.com/repos/alchemy-fr/Zippy/zipball/92c773f7bbe47fdb30c61dbaea3dcbf4dd13a40a",
                "reference": "92c773f7bbe47fdb30c61dbaea3dcbf4dd13a40a",
                "shasum": ""
            },
            "require": {
                "doctrine/collections": "~1.0",
                "ext-mbstring": "*",
                "php": ">=5.3.3",
                "symfony/filesystem": "^2.0.5|^3.0",
                "symfony/process": "^2.1|^3.0"
            },
            "require-dev": {
                "ext-zip": "*",
                "guzzle/guzzle": "~3.0",
                "phpunit/phpunit": "^4.0|^5.0",
                "symfony/finder": "^2.0.5|^3.0"
            },
            "suggest": {
                "ext-zip": "To use the ZipExtensionAdapter",
                "guzzle/guzzle": "To use the GuzzleTeleporter"
            },
            "type": "library",
            "extra": {
                "branch-alias": {
                    "dev-master": "0.2.x-dev"
                }
            },

Now composer install will use composer.lock instead of composer.json

Everyone has the same version of everything!

But I want the latest version of all the things!!!!

composer update

Cross your fingers

Updates folders and composer.lock