As discussedhere, the idea is to write a canonical article about Composer: what it is, how to install it (local and/or globally), and how to use it. It shouldn't be a complete copy ofComposer's own documentation, but should serve as an introduction to Composer for people who never used it before.

This article could be linked to by other articles, such asInstalling and Configuring Symfony andHow to Create and store a Symfony2 Project in Git (there might be more, I didn't search for other articles mentioning Composer very thoroughly).

This way, other articles only have to cover the basics, and can link to the canonical Composer-article for more information about Composer.