PHP cURL POST返回一个415不支持的媒体类型。

I've got a simple PHP script that sends an HTTP POST request via cURL, and expects a json string in response (would have loved to use an existing library like pecl_http/HTTPRequest for this, but can't). The call consistently fails with a 415 error - Unsupported Media Type. I think I'm not configuring cURL correctly, but after much searching, I can't find out what I'm doing wrong. Here's some code:I've got a simple PHP script that sends an HTTP