ubuntuにcomposerをインストール
参考
sudo apt install -y php libapache2-mod-php php-gd php-xml php-cli php-mbstring php-soap php-xmlrpc php-zip
curl -sS https://getcomposer.org/installer | php
sudo mv composer.phar /usr/local/bin/composer
sudo chmod +x /usr/local/bin/composer
source ~/.bashrc
確認
composer -v