PHP: Add a dimension to an array using array_map?

Question

I have an array and I want to add a dimension. I want to group it using the position column in the array

$view_rows = [];

Array
(
    [row] => Array
        (
            [0] => Array
                (
                    [position] => 1
                    [image_id] => 2809
                    [basename] => rj5ed2c90f609423.26673093.jpg
                )

            [1] => Array
                (
                    [position] => 1
                    [image_id] => 2808
                    [basename] => rj5ed2c8eccc9c06.91700011.jpg
                )

            [2] => Array
                (
                    [position] => 2
                    [image_id] => 2807
                    [basename] => rj5ed2c77ef32b76.96579137.jpg
                )
        )
)

After adding the dimension (group by location), it should look like this:

Array
(
    [rows] => Array
        (
            [1] => Array
                (
                    [0] => Array
                        (
                            [position] => 1
                            [image_id] => 2809
                            [basename] => rj5ed2c90f609423.26673093.jpg
                        )

                    [1] => Array
                        (
                            [position] => 1
                            [image_id] => 2808
                            [basename] => rj5ed2c8eccc9c06.91700011.jpg
                        )
                )

            [2] => Array
                (
                    [0] => Array
                        (
                            [position] => 2
                            [image_id] => 2807
                            [basename] => rj5ed2c77ef32b76.96579137.jpg
                        )
                )
        )
)

Is there a PHP function to do this? If not, I will use the good old looping method.

I did some research here ( Add Dimension in PHP array ), and I believe it can be achieve using array_map.

I've tried it, with no success (I'm close)

$new_array = array_map(function($x) {
    return [$x[0]['position'] => $x];
}, $view_rows);

Nick · Accepted Answer · 2021-01-05 01:03:07Z

1

Since you need to change the structure of the array, you can't use array_map, but you can use array_reduce to get the result you want:

$data['rows'] = array_reduce($data['rows'], function ($c, $a) {
    $c[$a['position']][] = $a;
    return $c;
}, array());

Output:

Array
(
    [rows] => Array
        (
            [1] => Array
                (
                    [0] => Array
                        (
                            [position] => 1
                            [image_id] => 2809
                            [basename] => rj5ed2c90f609423.26673093.jpg
                        )
                    [1] => Array
                        (
                            [position] => 1
                            [image_id] => 2808
                            [basename] => rj5ed2c8eccc9c06.91700011.jpg
                        )    
                )    
            [2] => Array
                (
                    [0] => Array
                        (
                            [position] => 2
                            [image_id] => 2807
                            [basename] => rj5ed2c77ef32b76.96579137.jpg
                        )    
                )    
        )    
)

Demo on 3v4l.org

answered Jan 5, 2021 at 1:03

Nick

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2 Comments

Marco Over a year ago

If I don't want to change the structure, but assign the values to a new array, can I use array_map? I've adapted your solution to do just that (assign the values to a new array), but I was just wondering if I could do that with array_map (I've try with no success)

Nick Over a year ago

@Marco, you can just change the assignment, use $new_array = array_reduce(...) instead of $data['rows'] = array_reduce(...). You can't easily use array_map because array_map gives you a result with the same structure as the input.

Parsa_Gholipour · Accepted Answer · 2021-01-06 12:30:26Z

1

@Nick answer works but the same thing can be achieved using a simple foreach loop easily so everyone can understand it.

$result = [];
foreach($data['rows'] as $row) {
    $result[$row['position']][] = $row;
}

edited Jan 6, 2021 at 12:30

answered Jan 5, 2021 at 1:14

Parsa_Gholipour

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