A walk through of various Composer tasks.
Composer is a dependency manager for PHP. It downloads public PHP packages (projects, libraries, etc) from Packagist.org.
Each step in this tutorial goes over basic Composer usage. The
composer.json files in each directory should be usable, and each directory
will have a README file explaining the concepts and commands for that step.
If you find any mistakes, please open an issue or create a pull request. Don't assume I know what I'm doing.™
The steps in this tutorial are based on building a Drupal 8 project with Composer, since that was the original motivation for the tutorial. However, most of what is explained is specific to Composer, not Drupal, so the information should still be relevant to any PHP project. And since the Drupal 8 use-case is more complex than simple "Hello, World!" functionality, it shows some of Composer's possibilities.
You need to have Composer installed. This will vary based on operating system. See the Composer docs for instructions.
It is important to note that the PHP version you use can matter. Composer uses
whichever version your command line uses. Run
php -v to see which version
you have. And, be consistent with your project. If your application and web
server will use PHP 7, upgrade your command line to use 7, as well.
In this tutorial, all commands begin with the
composer command. If this does
not work for you, you many have to manually setup an alias or move Composer's
.phar file. Composer's installation instructions, linked above, walk you
through that process.
There are two terms that cause some confusion and sometimes are used interchangeably - package and project. In this guide, package refers to anything Composer downloads. A PHP library, project, etc. Project refers to the project you are building.