没有composer：
curl -sS https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer //加载全局环境
安装yii2：
composer global require "fxp/composer-asset-plugin:~1.1.1"
composer create-project yiisoft/yii2-app-basic basic 2.0.6
链接：http://www.yiiframework.com/download/