Array reduce with associative array

Question

I have an array like this

 $filter_array = Array
    (
        [0] => Array
            (
                [fv_id] => 1
                [fv_value] => Red
                [filter_id] => 1
                [filter_name] => Color
            )

        [1] => Array
            (
                [fv_id] => 2
                [fv_value] => Blue
                [filter_id] => 1
                [filter_name] => Color
            )

    )

I would like to reduce the array by having filter_name and filter_id on top of array which is similar for all arrays.

$newArray = array_reduce($filter_array,function($carry,$item){

            $allFilterValues[] = array(
                'fv_id' => $item['fv_id'],
                'fv_value' => $item['fv_value'],
            );

             $formated_array = array(
                'filter_id' => $item['filter_id'],
                'filter_name' => $item['filter_name'],
                'filter_values' => $allFilterValues
            );
            return $formated_array;
        });

But I am just getting the last array iterations value on filter_values

Array
(
    [filter_id] => 1
    [filter_name] => Color
    [filter_values] => Array
        (
            [0] => Array
                (
                    [fv_id] => 2
                    [fv_value] => Blue
                )

        )

)

But I want the array be like this.

Array
(
    [filter_id] => 1
    [filter_name] => Color
    [filter_values] => Array
        (
                [0] => Array
                (
                    [fv_id] => 1
                    [fv_value] => Red
                ),

                [1] => Array
                (
                    [fv_id] => 2
                    [fv_value] => Blue
                )

        )

)

If you are merging on filter_id why do you abandon it as an array key? Are you sure you have the key names as they should be? It seems to me you should be using filter_id and filter_name as keys before each subgroup. — mickmackusa
– mickmackusa ♦, Commented Jul 16, 2017 at 8:02
On each iteration of array_reduce callback you should return $carry — u_mulder
– u_mulder, Commented Jul 16, 2017 at 8:04

u_mulder · Accepted Answer · 2017-07-16 08:23:47Z

3

On each iteration of array_reduce callback function must return current $carry value:

$newArray = array_reduce($filter_array,function($carry,$item){
    // create key so as to distinct values from each other
    $key = $item['filter_id'] . '-' . $item['filter_name'];

    // check if created key exists in `$carry`, 
    // if not - we init it with some data
    if (empty($carry[$key])) {
        $carry[$key] = [
            'filter_id' => $item['filter_id'],
            'filter_name' => $item['filter_name'],
            'filter_values' => []
        ];
    }

    // add values to `filter_values`
    $carry[$key]['filter_values'][] = [
        'fv_id' => $item['fv_id'],
        'fv_value' => $item['fv_value'],
    ];

    return $carry;
}, []);

// if you want to reindex `$newArray` from 0:
$newArray = array_values($newArray);

Update: if and only if in your $filter_array values of 'filter_id' and 'filter_name' are always the same you can simplify your code:

$newArray = [];
$first = true;
foreach ($filter_array as $item) {
    if ($first) {
        $first = false;
        $newArray = [
            'filter_id' => $item['filter_id'],
            'filter_value' => $item['filter_name'],
            'filter_values' => []
        ];
    }

    $newArray['filter_values'][] = [
        'fv_id' => $item['fv_id'],
        'fv_value' => $item['fv_value'],
    ];
}
echo'<pre>',print_r($newArray),'</pre>';

edited Jul 16, 2017 at 8:23

answered Jul 16, 2017 at 8:11

u_mulder

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4 Comments

phpnerd Over a year ago

Is any other array function makes things easier than this?

u_mulder Over a year ago

I suppose no. But you can rewrite this as a foreach.

phpnerd Over a year ago

Can you please tell me why you have passed [] after the callback argument in array_reduce?

u_mulder Over a year ago

Created a little update for code simplifying. As for your question - I pass [] as initial value of $carry. Of course, php can decide what initial value of $carry you use, so it's just my personal approach.

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