How can I merge arrays with along an identifier? - php

Question

I have two arrays like this:
$arr1 = ['yellow' => 1, 'red', => 5];
$arr2 = ['gray' => 3, 'black' => 8, 'orange' => 6, 'yellow' => 9];
And I want this result:
$merged = ['yellow' => [1, 'arr1'], 'red', => [5, 'arr1'], 'gray' => [3, 'arr2'], 'black' => [8, 'arr2'], 'orange' => [6, 'arr2'], 'yellow' => [9, 'arr2']];
But as I've read the documentation about array_merge(),it doesn't have such a option. Is there any function to do that for me?

Answer 1

This probably is what you are looking for:
<?php
$input = [
'arr1' => ['yellow' => 1, 'red' => 5],
'arr2' => ['yellow' => 10, 'gray' => 3, 'black' => 8, 'orange' => 6]
];
$output = [];
array_walk($input, function ($entry, $source) use (&$output) {
foreach ($entry as $key=>$val) {
$output[$key][] = [$val, $source];
}
});
print_r($output);
The output of above code obviously is:
Array
(
[yellow] => Array
(
[0] => Array
(
[0] => 1
[1] => arr1
)
[1] => Array
(
[0] => 10
[1] => arr2
)
)
[red] => Array
(
[0] => Array
(
[0] => 5
[1] => arr1
)
)
[gray] => Array
(
[0] => Array
(
[0] => 3
[1] => arr2
)
)
[black] => Array
(
[0] => Array
(
[0] => 8
[1] => arr2
)
)
[orange] => Array
(
[0] => Array
(
[0] => 6
[1] => arr2
)
)
)

Answer 2

Ok, it took me a bit longer to come up with this answer because you have a bug in your question. See the ',' behind 'red' in array 1.
$arr1 = ['yellow' => 1, 'red' => 5];
$arr2 = ['gray' => 3, 'black' => 8, 'yellow' => 3, 'orange' => 6];
$arrays = ['arr1','arr2'];
$merged = [];
foreach ($arrays as $array) {
foreach (${$array} as $color => $value) {
$merged[$color][] = [$value,$array];
}
}
echo '<pre>';
print_r($merged);
echo '</pre>';
To keep both values of 'yellow' I introduced an extra layer of arrays. I don't see how to keep them otherwise.
So the code was tested and returns:
Array
(
[yellow] => Array
(
[0] => Array
(
[0] => 1
[1] => arr1
)
[1] => Array
(
[0] => 3
[1] => arr2
)
)
[red] => Array
(
[0] => Array
(
[0] => 5
[1] => arr1
)
)
[gray] => Array
(
[0] => Array
(
[0] => 3
[1] => arr2
)
)
[black] => Array
(
[0] => Array
(
[0] => 8
[1] => arr2
)
)
[orange] => Array
(
[0] => Array
(
[0] => 6
[1] => arr2
)
)
)

Answer 3

Based on #arkascha answer a version that handle duplicates:
<?php
$input = [
'arr1'=> ['yellow' => 1,'red' => 5, 'black' => 4],
'arr2'=> ['gray' => 3,'yellow' => 3, 'black' => 8,'orange' => 6],
'arr3'=> ['orange' => 2]
];
$output = [];
array_walk($input, function ($entry, $source) use (&$output) {
foreach ($entry as $key=>$val) {
if(!array_key_exists($key, $output))
$output[$key] = [[$val, $source]];
else
$output[$key][] = [$val, $source];
}
});
echo print_r($output);
?>
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