1) Update your packages:
sudo apt-get update
2) Install the curl utility:
sudo apt-get install curl
3) Download the installer:
sudo curl -s https://getcomposer.org/installer | php
4) Move the composer.phar file:
sudo mv composer.phar /usr/local/bin/composer
5) Use the composer command to test the installation. If Composer is installed correctly, the server will respond with a long list of help information and commands:
user@localhost:~# composer
______
/ ____/___ ____ ___ ____ ____ ________ _____
/ / / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__ ) __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
/_/
Composer version 1.3.2 2017-01-27 18:23:41
Usage:
command [options] [arguments]
Options:
-h, --help Display this help message
-q, --quiet Do not output any message