Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project
depends on and it will manage (install/update) them for you.
Composer is not a package manager in the same sense as Yum or Apt are. Yes, it deals with "packages" or
libraries, but it manages them on a per-project basis, installing them in a directory (e.g.
vendor) inside your
project. By default it does not install anything globally. Thus, it is a dependency manager. It does however
support a "global" project for convenience via the global command.