PHP - Get highest value from json file

Question

I would like to get the highest value (y) from the following json-file.

   [{
     "name": "Time",
     "data": ["20:40", "20:45", "20:50"]
     },
     {
     "name": "Values",
     "data": [{
               "y": 5774,
               "v1": "Test1",
               "v2": "20:40"
              },
              {
               "y": 5555,
               "v1": "Test2",
               "v2": "20:45"
              },
              {
               "y": 5235,
               "v1": "Test3",
               "v2": "20:50"
              }]
            }]

Tried it with max()

$json_data = file_get_contents('file.json');
$json = json_decode($json_data, true);
$max_value = max($json["data"]);

echo $max["y"];

but I'm not getting any result...

you use wrong variable maybe should be $max_value['y'] non $max['y'] — Naumov
– Naumov, Commented Mar 12, 2016 at 21:07

C.Liddell · Accepted Answer · 2016-03-13 17:09:23Z

1

The following will retrieve the largest y value:

<?php
    $json_data = file_get_contents('a.json');
    $json = json_decode($json_data, true);
    $max_value = max($json[1]["data"]);

    echo $max_value['y'];
?>

And the following will retrieve the array with the largest y value:

<?php
$json_data = file_get_contents('a.json');
$json = json_decode($json_data, true);
$max_value = max($json[1]["data"]);

print_r($max_value);
?>

The problem with your script was you were trying to access a non-existent array on line 3 and you weren't echoing out the $max_value array correctly.

Warning

The above code only works because OP's JSON when converted to an array has the element he wants to order his array by as the first indexed value.

So like @MatsLindh stated below in the comments, if you had a value with the key of 'x' instead of 'y', no matter where it's located in the JSON provided it's still the lowest key value placing it as the first indexed value in the array when converted from JSON to an array.

You can still have mix-matched values in the JSON provided as long as the element you want to order by has the lowest value key placing it as the first element indexed in the array. For example:

   [{
     "name": "Time",
     "data": ["20:40", "20:45", "20:50"]
     },
     {
     "name": "Values",
     "data": [{
               "y": 5774,
               "v1": "Test1",
               "v2": "20:40",
               "Z" : 8000
              },
              {
               "y": 5555,
               "v1": "Test2",
               "v2": "20:45",
               "Abc": 6754
              },
              {
               "y": 5235,
               "v1": "Test3",
               "v2": "20:50",
               "v3": 6594
              }]
            }]

If the above JSON were passed through my first function it would return the desired result the OP was looking for, however.

   [{
     "name": "Time",
     "data": ["20:40", "20:45", "20:50"]
     },
     {
     "name": "Values",
     "data": [{
               "y": 5774,
               "v1": "Test1",
               "v2": "20:40",
                "a": 897
              },
              {
               "y": 5555,
               "v1": "Test2",
               "v2": "20:45"
              },
              {
               "y": 5235,
               "v1": "Test3",
               "v2": "20:50"
              }]
            }]

With this set of JSON, the element with the key "a" messes the count order up since it's placed at the beginning of the array.

Conclusion

If you know that the first value of the array generated from the JSON will always be what you want to count by then my code is fine. Otherwise it's better for you to use @MatsLindh's solution.

edited Mar 13, 2016 at 17:09

answered Mar 12, 2016 at 21:14

C.Liddell

1,07210 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Yousaf Hassan Over a year ago

Your answer is too good. Just add print_r($max_value['y']); and it will be perfect because he wants value for Y only, not the array.

C.Liddell Over a year ago

@YousafHassan Point taken. Revised answer. However I saw it best to use echo instead of print_r since $max_value['y'] always seems to be a string.

Yousaf Hassan Over a year ago

You are right, echo does the job, and yes i have voted up for your answer because its better than all others including mine.

MatsLindh Over a year ago

But this is not correct - the only reason why this works, is because the associative arrays are of the exact same size (and that the value you want to compare is the first value in the associative array). If there suddenly is one extra key in one of the assocative arrays (or the feed returns them in a different sequence - after all, they're just keys pointing to values), such as "x": 123 in the last element - then that will always be returned, regardless of the value of y.

C.Liddell Over a year ago

@MatsLindh Good point. Updated answer to include warning. However I still feel as if my answer was the best for OP since he/she had provided an example JSON set that follows a certain format.

|

Yousaf Hassan · Accepted Answer · 2016-03-12 21:14:09Z

0

The problem is that your json_decoded data isn't all in array form, but includes STD objects as well so another way to find the maximum value in your case is by using following algo.

$json_data = file_get_contents('file.json');
$json = json_decode($json_data, true);
$max_value = null;
foreach($json[1]->data as $dt){
    if($dt->y > $max_value)
        $max_value = $dt->y;
}
echo $max_value; // There it will output the highest value!

answered Mar 12, 2016 at 21:14

Yousaf Hassan

4944 silver badges14 bronze badges

Comments

Naumov · Accepted Answer · 2016-03-12 21:14:47Z

0

You can look this array in php format by var_dump function

$json_data = file_get_contents('file.json');
$json = json_decode($json_data, true);
$max_value = max($json["data"]);
var_dump($max_value);

and you need don't use max because this last element in array you need check exist key name = values for get values by foreach or array_map for analise you array in exist key name = values for exampel

$json_data = file_get_contents('file.json');
$json = json_decode($json_data, true);
foreach($json as $_js) {
   if($_js['name'] != 'Values') {
      continue;
   }
   foreach($_js['data'] as $__js) {
       echo $__js['y']; // or push to temporary variable
   }
}

answered Mar 12, 2016 at 21:14

Naumov

1,1879 silver badges22 bronze badges

Comments

MatsLindh · Accepted Answer · 2016-03-17 09:16:06Z

0

Since you're really trying to get the max value of a certain column in the array (doing just max($json[1]['data']) doesn't make sense by itself, as each element in that array is an associative array itself), you'll have to pick the values you want to find the maximum value of first:

$max_value = max(array_column($json[1]["data"], "y"));

This will extract each value from the y column of each element in the $json["data"] array, and return the largest value present (through max).

array_column was added in PHP 5.5, but you can emulate it through a small helper function if you're on an older version:

function array_column($array, $column) {
    $ret = array();
    foreach ($array as $elem) {
        $ret[] = $elem[$column];
    }
    return $ret;
}

edited Mar 17, 2016 at 9:16

answered Mar 12, 2016 at 21:13

MatsLindh

53.5k5 gold badges70 silver badges97 bronze badges

3 Comments

Naumov Over a year ago

$json['data'] not exist because he have array objects in context question

Naumov Over a year ago

why adding [1] after, maybe before adding [1][data]

MatsLindh Over a year ago

@Naumov Added it in the right place in the text, in the wrong place in the code. :-) You're my human compiler!

Collectives™ on Stack Overflow

PHP - Get highest value from json file

4 Answers 4

6 Comments

Comments

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

6 Comments

Comments

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related