无法通过Slim提交JSON POST数据

我使用Postman(在Chrome中)测试Slim调用,但无法弄清楚如何获取任何发布的JSON数据.

我提交原始JSON:

{"name":"John Smith", "age":"30", "gender":"male"}

使用内容类型:标题中的application/json

通过POST到:

http://domain/api/v1/users/post/test/

每次获取JSON数据的尝试都会产生致命错误(请参阅下面的代码注释)

add(new \Slim\Middleware\ContentTypes());


$app->group('/api/v1', function () use ($app) {

    $app->group('/users/post', function () use ($app) {

        $app->post('/test/', function () {

                print_r($app->request->headers); //no errors, but no output?

                echo "Hello!"; // outputs just fine

        $data = $app->request()->params('name'); //Fatal error: Call to a member function request() on a non-object
                $data = $app->request->getBody(); //Fatal error: Call to a member function getBody() on a non-object
                $data = $app->request->post('name'); //Fatal error: Call to a member function post() on a non-object
                $data = $app->request()->post(); //Fatal error: Call to a member function request() on a non-object

                print_r($data);
                echo $data;

        });

    });

});

$app->run();
?>

我错过了什么？

谢谢!