# php -r "copy('https://install.phpcomposer.com/installer', 'composer-setup.php');"
# php composer-setup.php
移动 composer.phar，这样 composer 就可以进行全局调用：
# mv composer.phar /usr/local/bin/composer
转自https://www.runoob.com/w3cnote/composer-install-and-usage.html