如何根据日期对结果进行排序

Question

我想抓住特定日期的所有事件。 我有一个事件结果：

{
    "response": {
        "2014-12-13": [
            {
                "id": "16",
                "event_name": "testing",
                "image": "images/Penguins.jpg",
                "event_date": "2014-12-13",
                "event_time": "02:10",
                "time_interval": "4",
                "location": "mohali",
                "event_type": "Rock",
                "detail": "sfdsf fgf ghb\t",
                "delivery": "dggh fghgfh\t\t",
                "status": "1"
            }
        ],
        "2014-12-18": [
            {
                "id": "15",
                "event_name": "hello",
                "image": "images/Desert.jpg",
                "event_date": "2014-12-18",
                "event_time": "02:10",
                "time_interval": "11",
                "location": "sss",
                "event_type": "Simple",
                "detail": "dss sd\t\t",
                "delivery": "asds sffs\t\t",
                "status": "1"
            },
            {
                "id": "14",
                "event_name": "dd",
                "image": "images/Tulips.jpg",
                "event_date": "2014-12-18",
                "event_time": "01:00",
                "time_interval": "sd",
                "location": "wed",
                "event_type": "Simple",
                "detail": "wdd\t\t\t",
                "delivery": "jbd\t\t\t",
                "status": "1"
            }
        ]
    }
}

我需要什么，我想用相同的密钥捕获每个日期以在IOS Web服务中捕获这些日期事件，LIKE

"event_date" :"2014-12-18": [    //this date have two result

"event_date" :"2014-12-13": [    //this date have oneresult

我试过这段代码：

 if(array_key_exists($data['event_date'],$sortArray))
                    {
                        $sortArray['response'][$data['event_date']][]=$data;
                    }
                        else
                    {
                        $sortArray['response'][$data['event_date']][]=$data;
                    }

那我该怎样做才能实现呢？

提前致谢