CODEWITHSUNDEEP
phparraysgroup-by
Jan Burger
Jan Burger

Reputation: 43

How do i group items by key in a multi dimension array with php

I have an array with data that i would want to group, example below:

[

{
    "date": "04-06-2016",
    "emmission": 3450
},
{
    "date": "04-06-2016",
    "emmission": 91
},
{
    "date": "09-02-2016",
    "emmission": 10
},
{
    "date": "04-06-2016",
    "emmission": 7
},
{
    "date": "19-04-2016",
    "emmission": 28
},
{
    "date": "08-05-2015",
    "emmission": 7
},
{
    "date": "04-06-2016",
    "emmission": 15
},
{
    "date": "04-06-2016",
    "emmission": 109
}

]

What i am trying to do is group them together by date and calculate the emmission value(sum by date);

thus the duplicated array like: { "date": "04-06-2016", "emmission": 3450 }

should only exists once and the emmission should be sum, i have tried almost everything from array_unique to array_search but still no luck.

Thanks

What i have now

public function unique_multidim_array($array, $key) { 
    $temp_array = array(); 
    $i = 0; 
    $key_array = array(); 

    foreach($array as $val) { 
        if (!in_array($val[$key], $key_array)) { 
            $key_array[$i] = $val[$key]; 
            $temp_array[$i] = $val; 

             // $temp_array[$i]['emmission'] += $array[$i]['emmission'];
        }

        $i++; 
    } 
    return $temp_array; 
} 

$this->unique_multidim_array($history, 'date');

With that i get unique dates but the emmission for the last element is zero

Upvotes: 3

Views: 47

Answers (1)

Jeff Puckett
Jeff Puckett

Reputation: 40861

one typo: "emmission" is spelled "emission"

a possible solution would use two loops. First to sum all the emissions grouped by date as a key, and then second to rebuild the object.

<?php
$json = '[

{
    "date": "04-06-2016",
    "emission": 3450
},
{
    "date": "04-06-2016",
    "emission": 91
},
{
    "date": "09-02-2016",
    "emission": 10
},
{
    "date": "04-06-2016",
    "emission": 7
},
{
    "date": "19-04-2016",
    "emission": 28
},
{
    "date": "08-05-2015",
    "emission": 7
},
{
    "date": "04-06-2016",
    "emission": 15
},
{
    "date": "04-06-2016",
    "emission": 109
}

]';

$arr_obj = json_decode($json);

// for each record, if date emission is set, then sum, else set emission
foreach ($arr_obj as $record)
  $dates[$record->date] = isset($dates[$record->date]) ? $dates[$record->date] + $record->emission : $record->emission;

// create array of objects
foreach ($dates as $key => $val)
  $obj_arr []= (object) array("date"=>$key,"emission"=>$val);

$json = json_encode($obj_arr);

echo $json;

Results in this output:

[{"date":"04-06-2016","emission":3672},{"date":"09-02-2016","emission":10},{"date":"19-04-2016","emission":28},{"date":"08-05-2015","emission":7}]

Upvotes: 1

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