Composer
php的包管理器，相关网址:
https://www.phpcomposer.com/
https://pkg.phpcomposer.com
https://getcomposer.org
https://packagist.org
中国镜像:
安装:
curl -sS https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer
测试：
composer --version
使用中国镜像:
composer config -g repo.packagist composer https://packagist.phpcomposer.com
常用命令:
安装
composer require 包
更新
composer update
移除
composer remove 包