Just as Node.JS has NPM or Ruby has Bundler, in PHP we have PHP Composer. It is a package manager that makes it easier for us to manage the depedencies of the libraries we work with our PHP Projects.
Installing PHP Composer
If you are a windows user, just download the installer always from their official site: https://getcomposer.org/Composer-Setup.exe
I personally work with Debian Linux, but the steps i am going to show you work similarly in Ubuntu and other Debian child distributions.
We download the PHP Composer
curl -sS https://getcomposer.org/installer -o composer-setup.php
We execute your installation
sudo php composer-setup.php --install-dir=/usr/local/bin --filename=composer
Executing the above will throw us the following over the command line.