Composer

Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will install and update them for you. We will learn:

  • how to install Composer
  • use it in new or existing project

Installation

Composer is an executable .phar file that you download and install as follows.

Windows

Use the official installer Composer-Setup.exe.

Linux, macOS

All you need is 4 commands, which you can copy from this page.

Further more, by copying into folder that is in system's PATH, Composer becomes globally accessible:

$ mv ./composer.phar ~/bin/composer # or /usr/local/bin/composer

Use in an existing project

To start using Composer in your project, all you need is a composer.json file. This file describes the dependencies of your project and may contain other metadata as well. The simplest composer.json can look like this:

{
	"require": {
		"nette/database": "^3.0"
	}
}

We're saying here, that our application (or library) depends on package nette/database (the package name consists of a vendor name and the project's name) and it wants the version that matches the ^3.0 version constraint.

So, when we have the composer.json file in the project root and we run:

composer update

Composer will download the Nette Database into directory vendor. It also creates a composer.lock file, which contains information about exactly which library versions it installed.

Composer generates a vendor/autoload.php file. You can simply include this file and start using the classes that those libraries provide without any extra work:

require __DIR__ . '/vendor/autoload.php';

$db = new Nette\Database\Connection('sqlite::memory:');

Creating New Project

New Nette project can be created by executing a simple command:

composer create-project nette/web-project name-of-the-project

Instead the name-of-the-project you should provide the name of the directory for your project and execute the command. Composer will fetch the nette/web-project repository from GitHub, which already contains the composer.json file, and right after that install the Nette Framework itself. The only thing which remains is to check write permissions on directories temp/ and log/ and you're ready to go.

PHP Version

Composer always installs those versions of packages that are compatible with the version of PHP you are currently using. Which, of course, may not be the same version as PHP on your web host. Therefore, it is useful to add information about the PHP version on the host to the composer.json file, and then only versions of packages compatible with host will be installed:

{
	"require": {
		...
	},
	"config": {
		"platform": {
			"php": "7.2"   # PHP verion on host
		}
	}
}

Packagist.org – Global Repository

Packagist is the main package repository, in which Composer tries to search packages, if not told otherwise. You can also publish your own packages here.

What If We Don't Want the Central Repository

If we have internal applications or libraries in our company, which cannot be hosted publicly on Packagist, we can create our own repositories for those project.

More on repositories in the official documentation.

Configuration

Composer is closely integrated with version control tool Git. If you do not use Git, it is necessary to tell it to Composer:

composer -g config preferred-install dist