For those that might have heard about the Composer package management system for PHP but haven't had the time to get into it, you should definitely check out this great primer from Dayle Rees.

Composer is something special in the world of PHP. It has changed the way we handle application dependencies, and quelled the tears of many PHP developers. You see, in the olden days, when you wanted to build an application that relied on third party dependencies you would have to install them with PEAR or PECL. These two dependency managers both have a very limited set of outdated dependencies and have been a thorn in the side of PHP developers for a long time. [...] Enter composer, king of the package managers.

He jumps right in and gets into the configuration (the composer.json file) and using it to describe the package. He shows how to set up "required" resources complete with version number information. There's a bit about setting up autoloading and classmaps too. He then moves on to getting the tool installed and using the composer.json definition to load in needed packages (and development ones if needed).