Question

我有一个多级JSON文件，我试图从中获取特定值，但我尝试的所有内容似乎都不起作用。

JSON:

   {  
   "mapVersion":59,
   "mapVersionString":"Fixed \"Me\" button. Fixed live updating of markers, Improved map performance...",
   "results":[  
      {  
         "ID":3644,
         "ParentID":null,
         "THINGSPEAK_PRIMARY_ID":"340896",
         "THINGSPEAK_PRIMARY_ID_READ_KEY":"ZGHNWCPCHD3HCNQM",
         "Label":"PurpleAir - Copperwood",
         "Lat":33.587254,
         "Lon":-112.196945,
         "PM2_5Value":"30.93",
         "State":null,
         "Type":"PMS5003+PMS5003+BME280",
         "Hidden":"false",
         "Flag":null,
         "DEVICE_LOCATIONTYPE":"outside",
         "DEVICE_BRIGHTNESS":"15",
         "isOwner":0,
         "A_H":null,
         "temp_f":"59",
         "humidity":"27",
         "pressure":"978.36",
         "AGE":0,
         "THINGSPEAK_SECONDARY_ID":"340899",
         "THINGSPEAK_SECONDARY_ID_READ_KEY":"CUMUMPCSVJM1L47F",
         "LastSeen":1514524202,
         "Version":"2.49j",
         "LastUpdateCheck":1514522192,
         "Uptime":"81220",
         "RSSI":"-64",
         "Stats":"{\"v\":30.93,\"v1\":32.82,\"v2\":34.24,\"v3\":33.03,\"v4\":20.49,\"v5\":22.6,\"v6\":21.8,\"pm\":30.93,\"lastModified\":1514524202452,\"timeSinceModified\":80183}"
      },
      {  
         "ID":3645,
         "ParentID":3644,
         "THINGSPEAK_PRIMARY_ID":"340901",
         "THINGSPEAK_PRIMARY_ID_READ_KEY":"VYY92GGQW8EAHU7F",
         "Label":"PurpleAir - Copperwood B",
         "Lat":33.587254,
         "Lon":-112.196945,
         "PM2_5Value":"31.63",
         "State":null,
         "Type":null,
         "Hidden":"false",
         "Flag":null,
         "DEVICE_LOCATIONTYPE":null,
         "DEVICE_BRIGHTNESS":null,
         "isOwner":0,
         "A_H":null,
         "temp_f":"59",
         "humidity":"27",
         "pressure":"978.39",
         "AGE":0,
         "THINGSPEAK_SECONDARY_ID":"340903",
         "THINGSPEAK_SECONDARY_ID_READ_KEY":"D5WDUE4DEKX6RNVW",
         "LastSeen":1514524232,
         "Version":"2.49j",
         "LastUpdateCheck":null,
         "Uptime":"81250",
         "RSSI":"-64",
         "Stats":"{\"v\":31.63,\"v1\":32.95,\"v2\":34.32,\"v3\":32.98,\"v4\":20.3,\"v5\":22.58,\"v6\":21.46,\"pm\":31.63,\"lastModified\":1514524232224,\"timeSinceModified\":79975}"
      }
   ]
}

我正试图达到统计数据下的“v”值，但我对如何做到这一点感到茫然。我已经json_decode尝试了$json_result->results->stats;，但我得到的只是一个空白的回报，所以我不知道我做错了什么（或没做错）。

任何帮助总是一个受欢迎的学习机会！

Answer 1

试试这个。您缺少result[0]索引号

$json_result=json_decode($a);
echo "<pre>";
print_r($json_result->results[0]->Stats);

Check your desired output

Answer 2

结果包含两个数组条目，统计信息区分大小写。

php > var_dump($json_result->results[0]->Stats);
string(141) "{"v":30.93,"v1":32.82,"v2":34.24,"v3":33.03,"v4":20.49,"v5":22.6,"v6":21.8,"pm":30.93,"lastModified":1514524202452,"timeSinceModified":80183}"

此外，如您所见，Stats包含JSON，需要对其进行解码：

php > $json_result->results[0]->Stats = json_decode($json_result->results[0]->Stats);
php > var_dump($json_result->results[0]->Stats);
object(stdClass)#4 (10) {
  ["v"]=>
  float(30.93)
  ["v1"]=>
  float(32.82)
  ["v2"]=>
  float(34.24)
  ["v3"]=>
  float(33.03)
  ["v4"]=>
  float(20.49)
  ["v5"]=>
  float(22.6)
  ["v6"]=>
  float(21.8)
  ["pm"]=>
  float(30.93)
  ["lastModified"]=>
  int(1514524202452)
  ["timeSinceModified"]=>
  int(80183)
}
php > var_dump($json_result->results[0]->Stats->v);
float(30.93)

从PHP中的多级JSON获取变量

2 个答案: