问致命错误:找不到'OpenCloud\Rackspace‘类

EN

# Install Composer
curl -sS https://getcomposer.org/installer | php

# Require php-opencloud as a dependency
php composer.phar require rackspace/php-opencloud:dev-master

Fatal error: Class 'OpenCloud\Rackspace' not found in /var/www/example/Project/sites/all/libraries/php-opencloud/test.php on line 7

<?php

require 'vendor/autoload.php';
use OpenCloud\Rackspace;

// 1. Instantiate a Rackspace client.
$client = new Rackspace(Rackspace::US_IDENTITY_ENDPOINT, array(
    'username' => getenv('Axxxxxxx'),
    'apiKey'   => getenv('abcxxxxxxxxxxxxxxxxxxxx')
));

print_r($client); die('!!');