Oauth 2.0令牌生成，使用php作为服务器端授予类型客户端凭据

Question

Token.php:

$server->handleTokenRequest(OAuth2\Request::createFromGlobals())->send();

Command line:

curl -u testclient:testpass http://localhost/oauth2/token.php -d 'grant_type=client_credentials'

I am following this tutorial:

http://bshaffer.github.io/oauth2-server-php-docs/cookbook/

I am getting an error "Grant type was not specified"