> wget https://getcomposer.org/composer.phar> mv composer.phar composer
> chmod +x composer
全局：
sudo mv composer /usr/local/bin
测试：
composer --version
> wget https://getcomposer.org/composer.phar> mv composer.phar composer
> chmod +x composer
全局：
sudo mv composer /usr/local/bin
测试：
composer --version