Linux 平台可以使用以下命令来安装：

# php -r "copy('https://install.phpcomposer.com/installer', 'composer-setup.php');"

# php composer-setup.php

All settings correct for using ComposerDownloading...Composer (version 1.6.5) successfully installed to: /root/composer.pharUse it: php composer.phar

移动 composer.phar，这样 composer 就可以进行全局调用：

# mv composer.phar /usr/local/bin/composer

切换为国内镜像：

# composer config -g repo.packagist composer https://packagist.phpcomposer.com

更新 composer：

# composer selfupdate

chmod 755 composer.phar