php: combine multiple arrays value into one array preserving keys

Question

I have multiple arrays structured like these:

$array1 = ["aaa" => 1, "bbb" => 1];
$array2 = ["aaa" => 12, "bbb" => 12];
$array3 = ["bbb" => 15, "ccc" => 15];

meaning:

every array has the same value for each key (eg: array1 has value "1" for every item in the array) but there are no arrays sharing the same value (eg: if array1 has value 1, then none of the other arrays has value = 1)
the arrays may or may not share the same keys

I need to combine these arrays in a way that the final result is something like this:

$result = [
    "aaa" => [1,12],
    "bbb" => [1,12,15],
    "ccc" => [15],
];

meaning:

the final array must contain all the keys from the previous arrays
the value of the key is an array composed of all the values of the previous arrays that shared the same key

I know it's a bit messy, but I hope it is clear enough. I'm struggling to build the $result array. I tried merge, combine, intersect, but none of them seems to work. Is there a way to build the $result array without using a loop?

Thanks

Is there a way to build the $result array without using a loop? The short answer is no, there will always be some kind of 'looping' involved, whether in plain sight or hidden (in functions). — berend
– berend, Commented Sep 27, 2021 at 15:39
I don't think there's any built-in merging function that will do this. The loop should be pretty straightforward. — Barmar
– Barmar, Commented Sep 27, 2021 at 15:42
Start with foreach ([$array1, $array2, $array3] as $array) { foreach ($array as $key => $value) { ... } }. The ... pushes the value into the appropriate element of $result. — Barmar
– Barmar, Commented Sep 27, 2021 at 15:43

Philippe · Accepted Answer · 2021-09-27 15:46:43Z

0

Does it match your goal ?

<?php
    $array1 = ["aaa" => 1, "bbb" => 1];
    $array2 = ["aaa" => 12, "bbb" => 12];
    $array3 = ["bbb" => 15, "ccc" => 15];

    $array = array_merge_recursive($array1, $array2, $array3);
    
    print_r($array);
?>

outputs

Array
(
    [aaa] => Array
        (
            [0] => 1
            [1] => 12
        )

    [bbb] => Array
        (
            [0] => 1
            [1] => 12
            [2] => 15
        )

    [ccc] => 15
)

answered Sep 27, 2021 at 15:46

Philippe

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2 Comments

Lou Nik Over a year ago

Hi. thank you a lot, this looks to me like the best solution. Note: array_merge_recursive works well only with string keys, if you have numeric strings or int as keys, array_merge_recursive won't keep them. It's not an issue in my case anyway, thanks again

Philippe Over a year ago

Glad to read it, thanks for your feedback and precision. In fact, don't repeat it to anyone, but I discover this function with you :D Happy coding !

Tuan Dao · Accepted Answer · 2021-09-27 15:49:27Z

0

Merge all of array into an mergedArray. Then use 2 foreach to set it.

<?php

$array1 = ["aaa" => 1, "bbb" => 1];
$array2 = ["aaa" => 12, "bbb" => 12];
$array3 = ["bbb" => 15, "ccc" => 15];

$mergedArray = [$array1, $array2, $array3];


$result = [];
foreach ($mergedArray as $array) {
    foreach ($array as $key => $item) {
        $result[$key][] = $item;
    }
}

echo '<pre>';
print_r($result);
echo '</pre>';
exit;

?>

The result:

Array
(
    [aaa] => Array
        (
            [0] => 1
            [1] => 12
        )

    [bbb] => Array
        (
            [0] => 1
            [1] => 12
            [2] => 15
        )

    [ccc] => Array
        (
            [0] => 15
        )

)

answered Sep 27, 2021 at 15:49

Tuan Dao

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