How to access JSON object without knowing its name (and that is not in an array)

Question

My problem is rather simple, at least I hope so, but I just cannot find the solution. I have a JSON string, which I got from a get request to a server.

Exemple of my JSON :

"body":[
{
   "_id":"70:ee:50:05:00:aa",
   "place":{
      "location":[
         2.4358958,
         49.503012
      ],
      "altitude":89,
      "timezone":"Europe/Paris"
   },
   "mark":8,
   "measures":{
      "02:00:00:04:f8:6a":{
         "res":{
            "1431926951":[
               7.9,
               83
            ]
         },
      "type":[
         "temperature",
         "humidity"
         ]
      },
      "70:ee:50:05:00:aa":{
         "res":{
            "1431932787":[
               1009.4
            ]
         },
         "type":[
            "pressure"
         ]
      }
  },
  "modules":[
     "02:00:00:04:f8:6a"
  ]
},

I need to accessthe temperature value, so following this example I would do this : $value = body->measures->02:00:00:04:f8:6a->res->1431926951[0].

I know i can't just do this : measures->02:00:00:04:f8:6a. The cool thing is that this difficulty can be solved doing this : $module = body->modules[0] and then I can use this variable. So it would look like this : body->measures->$module->res->1431926951[0].

What I can't seem to do though is the final step : res->1431926951[0]. This number seem completely random I can't find this value anywhere else in the JSON so I can't use the same trick I did for 02:00:00:04:f8:6a. So my question is how can I access the first value of the array located inside the object "1431926951" without knowing its name ?

Thank you very much for taking the time to help me.

EDIT : here is the code I am using in PHP

$results = json_decode($resp);
foreach($results->body as $result){
    $id = $result->_id;
    $lat = $result->place->location[0];
    $lng = $result->place->location[1];
    $module = $result->modules[0];
    $type = $result->measures->$module->type[0];
    $value = "1431926951";
    //$test = $result->measures->$module->res->$value[0];
    /*$res = $result->measures[$result->measures[0]]->res;
    $test = $res[Object.keys($res)[0]][0];*/
    echo 'Id: '.$id.' - Lat: '.$lat.' - Lng: '.$lng.' - test: '.$test."<br>";
}

Answer 1

var jsonvar = { key: { key1: "value 1", key2: "value 2" } };
var key = Object.keys(jsonvar)[0];

This is how we can get the json key from the given json object using javascript.

Explaination: Lets say you have a json variable in javascript named jsonvar which is holding some json data. Now, to access the first key contained in parent json, then make use of array as shown above.

Object.keys(jsonvar)[0]

will return the json key: "key". We are accessing the jsonvar to access the first key which corresponds to position [0].

Hope this could solve your problem.

Answer 2

You can access with the Object.keys to the name of the property in JavaScript.

var res = obj.body.measures[ obj.body.modules[0] ].res;
console.log( res[ Object.keys(res)[0] ][0]); // prints 7.9

See demo

EDIT (PHP version, only 2 lines):

With PHP is the same but using key and stdClass (json_decode returns stdClass)

$res = $obj->body->measures->{ $obj->body->modules[0] }->res;
echo $res->{ key( (array) $res ) }[0]; // prints 7.9

See demo

Hope help.

Answer 3

Here's how I did it in PHP:

<?php

$ob = '
{
"body":[
{
   "_id":"70:ee:50:05:00:aa",
   "place":{
      "location":[
         2.4358958,
         49.503012
      ],
      "altitude":89,
      "timezone":"Europe/Paris"
   },
   "mark":8,
   "measures":{
      "02:00:00:04:f8:6a":{
         "res":{
            "1431926951":[
               7.9,
               83
            ]
         },
      "type":[
         "temperature",
         "humidity"
         ]
      },
      "70:ee:50:05:00:aa":{
         "res":{
            "1431932787":[
               1009.4
            ]
         },
         "type":[
            "pressure"
         ]
      }
  },
  "modules":[
     "02:00:00:04:f8:6a"
  ]
}
]
}';

//turn the json into a PHP object
$ob = json_decode($ob);

//pre-defined array of known module names
$modules = array("02:00:00:04:f8:6a", "70:ee:50:05:00:aa");

//loop through each moduke
foreach($modules as $module){
    //get the 'res' property for that module
    $res = $ob->body[0]->measures->$module->res;
    //get a list of the object properties
    $properties = get_object_vars($res);
    //select the first property (we don't know the name) uising the current() function
    $firstProperty = current($properties);
    //and print it out
    echo "The first property of $module is: ";
    print_r($firstProperty);
    echo "<br/><br/>";
}