如何在向webhook发送答案时对电报Bot API执行请求？

the Telegram API say:

If you're using webhooks, you can perform a request to the Bot API while sending an answer to the webhook.

i try to do it by this simple code:

header('Content-Type: application/x-www-form-urlencoded');
$content = http_build_query(array(
    'method' => 'sendMessage',
    'chat_id' => 123,
    'text' => 'test 123'
));
file_put_contents("php://output", $content); // or echo $content;

but i can't see any response in the robot.

the Telegram update robot API in last day and now support JSON response. so we can change the code:

header('Content-Type: application/json');
echo json_encode(array(
    'method'=>'sendMessage',
    'text'=>'test 123',
    'chat_id'=>123,
));
die;

and it works for me!