composer class not found
composer成功后，跑对应的例子，提示 Class 'xxxx' not found
原因是没有启用autoload：
<?php
require __DIR__ . '/vendor/autoload.php';
optimize automatic loading
composer dump-autoload --optimize
ref：https://github.com/aliyun/openapi-sdk-php/blob/master/docs/en-US/1-Installation.md