https://www.digitalocean.com/community/tutorials/how-to-install-and-use-composer-on-debian-9
Remove System Composer
sudo apt remove composer
Update System
sudo apt update
Install Requiriments
sudo apt install curl php-cli php-mbstring git unzip
Get Composer
cd ~
curl -sS https://getcomposer.org/installer -o composer-setup.php
Install Composer
sudo php composer-setup.php --install-dir=/usr/local/bin --filename=composer
Check Instalation
composer -v