composer

$ cd ~
$ sudo curl -sS https://getcomposer.org/installer | sudo php
$ sudo mv composer.phar /usr/local/bin/composer
$ sudo ln -s /usr/local/bin/composer /usr/bin/composer

then you can run 
$ sudo composer install


以上是安裝 composer 的步驟，要注意當時使用的 php 版本