How to get "any" mongodb result key from an object

Question

I have a PHP script that returns the result in CSV format:

# cat query.php
<?php

include '../misc.php';
$values=$_GET?$_GET:$_POST;

{
  $ts = isset($values['t'])?strtotime($values['t']):strtotime("-1 hour");
  $result=Query('iot.data',['key' => $values['key'], 'timestamp' => array('$gte' => $ts)],['projection' => array('_id' => 0, 'timestamp' => 1, $values['col'] => 1), 'sort' => array('timestamp' => 1)]);

    if ($values['col'] == 'temp1') echo "Timestamp, Temperature\n";
    if ($values['col'] == 'BusV2') echo "Timestamp, Battery V\n";
    if ($values['col'] == 'uv1') echo "Timestamp, UV\n";


  foreach ($result as $r) { 
    $d = date('c',$r->timestamp);
    if (isset($r->temp1)) echo "$d, $r->temp1\n";
    if (isset($r->BusV2)) echo "$d, $r->BusV2\n";
    if (isset($r->uv1)) echo "$d, $r->uv1\n";
  };
};

With the col parameter, I can decide which key will be returned with a timestamp.

How can I get the desired result without these IFs inside the foreach loop?

How do I encode something like:

foreach ($result as $r) { 
    $d = date('c',$r->timestamp); 
    echo "$d, $r->$values['col']\n" // where object $r key comes from variable 'col'
}

This will not help if I changed this foreach to: foreach ($result as $r => $v) {

because it $vdoes not receive the key value $r, $vnow what $rcame before ...

Result print_r($v);

stdClass Object
(
    [temp1] => 25.2
    [timestamp] => 1470304854
)

Answer 1

If I understand what you want to achieve, you should use:

foreach ($result as $r) { 
    $d = date('c',$r->timestamp);    
    echo "$d, " . $r->{$values['col']} . "\n";
};

, mongo stdClass Object, , ->, $r[$values['col']] 500.