接收JSON回调？

我正在尝试使用Coinbase的API（）在比特币支付后接收对我的站点的回调。但是，我不确定如何将收到的JSON回调放入变量中，以便使用回调的信息

Coinbase的示例回调是：

{
"order": {
    "id": "5RTQNACF",
    "created_at": "2012-12-09T21:23:41-08:00",
    "status": "completed",
    "total_btc": {
        "cents": 100000000,
        "currency_iso": "BTC"
    },
    "total_native": {
        "cents": 1253,
        "currency_iso": "USD"
    },
    "custom": "order1234",
    "receive_address": "1NhwPYPgoPwr5hynRAsto5ZgEcw1LzM3My",
    "button": {
        "type": "buy_now",
        "name": "Alpaca Socks",
        "description": "The ultimate in lightweight footwear",
        "id": "5d37a3b61914d6d0ad15b5135d80c19f"
    },
    "transaction": {
        "id": "514f18b7a5ea3d630a00000f",
        "hash": "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b",
        "confirmations": 0
    }
}
}

我试过使用

$json = $_POST["order"]

检索它，但它不起作用。

尝试使用

$get = file_get_contents("php://input");

试用

$get = file_get_contents("php://input");