Php 通过服务器获取JSON数据时出现问题？

我正在使用Tropo Web API，为了从聊天应用程序获取结果，我将JSON响应重定向到服务器端PHP文件（），JSON响应正确，但我无法使用PHP从中获取数据， JSON响应如下所示

{
    "result": {
        "actions":
            [
                {
                    "attempts": 2, 
                    "concept": "mumbai", 
                    "confidence": 100, 
                    "disposition": "SUCCESS", 
                    "interpretation": "mumbai", 
                    "name": "city", 
                    "utterance": "mumbai", 
                    "value": "mumbai", 
                    "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?><result grammar=\"1@6ac61bfd.vxmlgrammar\"><interpretation grammar=\"1@6ac61bfd.vxmlgrammar\" confidence=\"100\"><instance>mumbai<\/instance><input mode=\"voice\" confidence=\"100\" timestamp-start=\"1970-01-01T00:00:00.000\" timestamp-end=\"1970-01-01T00:00:00.000\">mumbai<extensions><word-confidence> 100 <\/word-confidence><\/extensions><\/input><extensions><probability> 0 <\/probability><nl-probability> 0 <\/nl-probability><necessary-word-confidence> 0 <\/necessary-word-confidence><\/extensions><\/interpretation><\/result>\r\n\r\n"
                }, 
                {
                    "attempts": 1, 
                    "concept": "cricket", 
                    "confidence": 100, 
                    "disposition": "SUCCESS", 
                    "interpretation": "cricket", 
                    "name": "sports", 
                    "utterance": "cricket", 
                    "value": "cricket", 
                    "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?><result grammar=\"2@6ac61bfd.vxmlgrammar\"><interpretation grammar=\"2@6ac61bfd.vxmlgrammar\" confidence=\"100\"><instance>cricket<\/instance><input mode=\"voice\" confidence=\"100\" timestamp-start=\"1970-01-01T00:00:00.000\" timestamp-end=\"1970-01-01T00:00:00.000\">cricket<extensions><word-confidence> 100 <\/word-confidence><\/extensions><\/input><extensions><probability> 0 <\/probability><nl-probability> 0 <\/nl-probability><necessary-word-confidence> 0 <\/necessary-word-confidence><\/extensions><\/interpretation><\/result>\r\n\r\n"
                }
            ], 
        "callId": "b546e03db1ccfd2f0e8c58d970539501", 
        "complete": true, 
        "error": null, 
        "sequence": 1, 
        "sessionDuration": 11, 
        "sessionId": "ed6abc73b9c434385ea8cd8004c9ed0c", 
        "state": "ANSWERED"
    }
}

---

但是我在变量$value中得到null。如何获得城市和体育的价值…？

这是因为

$result->result->actions

是一个数组。尝试

$result->result->actions[0]->value

编辑代码块以强调数组。

$json = file_get_contents("php://input");
$result = json_decode($json);
$value =$result->result->actions->value;