Calculating max and min array values is giving wrong results

Question

I have this array with wind speeds:

 Array
(
[0] => 14
[1] => 15
[2] => 16
[3] => 11
[4] => 9
[5] => 7
[6] => 8
)

When I try to calculate max and min values, instead of the expected max=16 and min=7, it returns max=11 and min=9. To make things even more difficult to understand, if the array is composed only of 2 digit wind speeds or only of 1 digit speeds, the max and min values are returned correctly, so this problem only occurs when there are 2 digit and 1 digit speed values at the same time in the array!

I tried many solutions found here like adding a leading zero, number formating, sorting the array, etc, but... no results!

The $wind_speed values are parsed from a json url like this

 {
     "type": "Feature",
     "geometry": {
         "type": "Point",
         "coordinates": [
             -9.13,
             39.4,
             100
         ]
     },
     "properties": {
         "meta": {
             "updated_at": "2021-01-26T20:39:53Z",
             "units": {
                 "wind_speed": "km/h"
             }
         },
         "timeseries": [
             {
                 "time": "2021-01-26T22:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 16
                         }
                     }
                 }
             },
             {
                 "time": "2021-01-26T23:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 9
                         }
                     }
                 }
             },
             {
                 "time": "2021-01-27T00:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 7
                         }
                     }
                 }
             }
         ]
     }
 }

From Json I get

 $decoded = json_decode($rawData, true); 
 $timeseries=$decoded['properties']['timeseries'];
 $total_events=count($timeseries);  

 for($k=0;$k<$total_events;$k++){       
 $wind_speed[$k]=$decoded['properties']['timeseries'][$k]['data']['instant']['details']['wind_speed']';
 ...

and then the array is created with a foreach loop,

 $i = 0;
 $wind= array();
 foreach ($wind_speed as $windt) {
 $wind[] = $windt;
 if(++$i > $total_events) break;
 }
 ....
 print_r($wind); // shows expected values and is correct

 echo(min($wind)); //shows correct result if array contains ONLY 2 digit or ONLY 1 digit wind speeds
 echo(max($wind)); // and shows wrong result if array contains BOTH 2 digit and 1 digit wind speeds
 ....

Is there any reason for this to happen?

Answer 1

This returns the correct min/max:

<?php

$decoded = json_decode('{
     "type": "Feature",
     "geometry": {
         "type": "Point",
         "coordinates": [
             -9.13,
             39.4,
             100
         ]
     },
     "properties": {
         "meta": {
             "updated_at": "2021-01-26T20:39:53Z",
             "units": {
                 "wind_speed": "km/h"
             }
         },
         "timeseries": [
             {
                 "time": "2021-01-26T22:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 16
                         }
                     }
                 }
             },
             {
                 "time": "2021-01-26T23:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 9
                         }
                     }
                 }
             },
             {
                 "time": "2021-01-27T00:00:00Z",
                 "data": {
                     "instant": {
                         "details": {
                             "wind_speed": 7
                         }
                     }
                 }
             }
         ]
     }
 }', true);

 $wind_speed = [];
 foreach ($decoded['properties']['timeseries'] as $item) {
    $wind_speed[] = $item['data']['instant']['details']['wind_speed'];
 }

 echo "Min -> ".min($wind_speed)."\n";
 echo "Max -> ".max($wind_speed)."\n";

Output is:

Min -> 7
Max -> 16

If for some reason you have a usecase that does not work, please give us the exact Json.