Composer is a dependency manager tool for PHP. It installs and updates the libraries for your project. It is not a package manager like yum command or apt-get command. It is designed to use with each individual project like Mediawiki or your own custom app written in PHP. There are many open source projects and frameworks written in php use Composer to manage and install their packages and dependencies. So getting familiar with Composer is quite important. In this tutorial you will learn how to install composer globally on Debian or Ubuntu Linux server.