Not able to extract variable values from json array data after encoding array using json_encode in php

Question

I am trying to transfer some data from PHP to javascript in json format. The data is actually two fields of a database table, 'humidity' & 'temperature'. After fetching the data from database in php in the form of an array ($wData), I encode it into json using json_encode, get the reference in a js var (WData) and pass it to a js function as parameter (jData).

The data after being received in js function appears fine. But when I try to extract the 'humidity'´or 'temperature' values from it using jData.humidity OR jData.temperature, it shows 'undefined' result in console. One more thing is that the 'humidity'´or 'temperature' variables do not appear in the IDE that they should after I write 'jData.'

Though if I put jData[0], it shows values of both variables. I need to get values of both variables separately because I need to use them to display their own values in a chart.

But as results show that data is at least received. So my question is how to get values of both 'humidity' & 'temperature' in different variables like ones are in my js code.

Here is my code:

PHP CODE

$result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
$WData = $stmt->fetchAll();

/*
echo "<pre>".print_r($WData, true)."</pre>"; 
die();
*/

?>

<script>
  var WData = <?php print_r(json_encode($WData));?>;
//  console.log(WData);
  dspChrt(WData);
</script>

JS CODE

 function dspChrt(jData) { 

    //jData = JSON.parse(wData); 
    console.log(jData[0]); //outputs value
    console.log(jData.humidity); //outputs 'undefined'

    hum = jData.humidity;
    tem = jData.temperature;
    humArray.shift();
    humArray.push(hum);
    temArray.shift();
    temArray.push(tem);

".print_r($WData, true).""; die();

Array
(
    [0] => Array
        (
            [humidity] => 77.7
            [temperature] => 22.1
        )

    [1] => Array
        (
            [humidity] => 81.7
            [temperature] => 28.1
        )

    [2] => Array
        (
            [humidity] => 67.21
            [temperature] => 28.9
        )

    [3] => Array
        (
            [humidity] => 11.11
            [temperature] => 22.11
        )

    [4] => Array
        (
            [humidity] => 15
            [temperature] => 77.7
        )

    [5] => Array
        (
            [humidity] => 15
            [temperature] => 77.7
        )

console.log(jData); output

[0…999]

[0…99]

0: Object { humidity: "77.7", temperature: "22.1" }

    1: Object { humidity: "81.7", temperature: "28.1" }
    
    2: Object { humidity: "67.21", temperature: "28.9" }
    
    3: Object { humidity: "11.11", temperature: "22.11" }
    
    4: Object { humidity: "15", temperature: "77.7" }
    
    5: Object { humidity: "15", temperature: "77.7" }

console.log(jData[0]); output

   {
  "humidity": "77.7",
  "temperature": "22.1"
}

console.log(jData.humidity) output

undefined

console.log(jData.humidity[]); output

SyntaxError: expected expression, got ']'

It's because `jData.humidity` is undefiined, that key doesn't exist in your object. If you did `jData[0].humidity` you would get the humidity for your first row — GrumpyCrouton, Sep 25 '18 at 13:02
I remember in one of your other questions you said you needed this for a chart.js chart, which means I know you need the value for these columns independantly (depending on how you're displaying data). In PHP you have the function `array_column()` which extracts all the values to it's own array; javascript doesn't have an alternative to this but I've had luck with [this function](https://stackoverflow.com/a/7848073/5827005), where you would basically do `var humArray = getCol(jData, 'humidity');`, then you'd be able to access them in order by `humArray[0]`, `humArray[1]`, etc — GrumpyCrouton, Sep 25 '18 at 13:07
i read this function and come back if any question. But thanks a lot for being so helpful as I think you potentially gave answer of my next question because I need to get them in order by humArray[0], humArray[1] to display these in a graph form. — XCeptable, Sep 25 '18 at 13:21

Not able to extract variable values from json array data after encoding array using json_encode in php

0 Answers0