Replace column values in a 2d array using a flat array of replacement values

Question

I have a two-dimensional array of this format:

$oldArr = [
    0 => [
        "color" => "red",
        "shape" => "circle",
        "size" => "small",
    ],
    1 => [
        "color" => "green",
        "shape" => "square",
        "size" => "large",
    ],
    2 => [
        "color" => "yellow",
        "shape" => "triangle",
        "size" => "large",
    ],
];

And a one-dimensional array of this format:

$newVals = [
    0 => "large",
    1 => "large",
    2 => "small",
];

I'm attempting to use str_replace() to iterate through each "size" value in $oldArr, and replace it with the value in $newVals that matches its position. Since these arrays will always have the same number of top-level key-value pairs, I'm basically trying to take $newVals and map it onto each $oldArr["size"] value. The end result should be

$newArr = [
    0 => [
        "color" => "red",
        "shape" => "circle",
        "size" => "large",
    ],
    1 => [
        "color" => "green",
        "shape" => "square",
        "size" => "large",
    ],
    2 => [
        "color" => "yellow",
        "shape" => "triangle",
        "size" => "small",
    ],
];

Can anyone recommend the best way to go about this? I've attempted a str_replace in a foreach loop, but it hasn't worked:

foreach($oldArr as $entity):

    str_replace($entity['size'], $newVals, $entity);

endforeach;

Kind of, sort of related: Replace multidimensional array values with one-dimensional array — mickmackusa
– mickmackusa ♦, Commented Apr 12, 2023 at 7:41

Rizier123 · Accepted Answer · 2016-03-08 16:50:21Z

1

You can use array_map() and loop through both arrays at once and instead of using the size value of your original array, you just use the new one, e.g.

$result = array_map(function($old, $new){
    return ["color" => $old["color"], "shape" => $old["shape"], "size" => $new];
}, $oldArr, $newVals);

answered Mar 8, 2016 at 16:50

Rizier123

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Comments

alexander.polomodov · Accepted Answer · 2016-03-08 16:49:10Z

1

You can use this code:

<?php

$oldArr = [
    0 => [
        "color" => "red",
        "shape" => "circle",
        "size" => "small",
    ],
    1 => [
        "color" => "green",
        "shape" => "square",
        "size" => "large",
    ],
    2 => [
        "color" => "yellow",
        "shape" => "triangle",
        "size" => "large",
    ],
];


$newVals = [
    0 => "large",
    1 => "large",
    2 => "small",
];

$newArr = array();
foreach($oldArr as $key => $entity){
    $newEntity = $entity;
    $newEntity['size'] = $newVals[$key];
    $newArr[$key] = $newEntity;
}

var_dump($newArr);

answered Mar 8, 2016 at 16:49

alexander.polomodov

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Comments

mickmackusa · Accepted Answer · 2023-04-12 10:09:44Z

array_walk() modifying the original array: (Demo)

array_walk(
    $oldArr,
    fn(&$row, $i) => $row['size'] = $newVals[$i]
);
var_export($oldArr);

foreach() modifying the original array: (Demo)

foreach ($oldArr as $i => ['size' => &$size]) {
    $size = $newVals[$i];
}
var_export($oldArr);

foreach() to produce a new array: (Demo)

$result = [];
foreach ($oldArr as $i => $row) {
    $row['size'] = $newVals[$i];
    $result[] = $row;
}
var_export($result);

array_map() to synchronously iterate both arrays and avoid declaring a result array: (Demo)

var_export(
    array_map(
        fn($row, $size) => array_replace($row, ['size' => $size]),
        $oldArr,
        $newVals
    )
);

*Because the rows to be joined contain associative/non-numeric keys, array_merge() and array_replace() behave identically. The array union operator (+) can not be used for this task because it retains the left side elements where both payloads contain the same key -- in other words, there would be no change.

array_replace_recursive() after mutating the new values into a 2d array: (Demo)

var_export(
    array_replace_recursive(
        $oldArr,
        array_map(fn($size) => ['size' => $size], $newVals)
    )
);

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