composer update foo/bar
composer.json的情况下安装库composer require "foo/bar:1.0.0"
composer create-project doctrine/orm path 2.2.0
http://www.phpcomposer.com/5-features-to-know-about-composer-php/
后面还有两条不太理解就没有摘抄过来了
原文：http://www.cnblogs.com/isuben/p/7060896.html