Merge all subarrays on second level of a multidimensional array [duplicate] - php

Question

This question already has answers here:
How to array_merge_recursive() an array?
(2 answers)
Closed 5 months ago.
I need to find a way to combine elements by key in a new array, such that I end up with just one key containing all values for that key (found elsewhere in the parent array). This will make more sense when you see the example below:
Array
(
[0] => Array
(
[AAA] => Array
(
[0] => F104_f58f85f9dbbe1ce083ca09a6f9ace679
[1] => F104_480e9f231b2b5a138f8aa5570ffa8634
[2] => F104_d5fde0ad2499052e0eae6dec451f9385
)
[BBB] => Array
(
[0] => F44_e2e052e7b78abbae02ffcf7413302a0c
[1] => F44_4d4da736509babebba7433b203b16753
)
)
[1] => Array
(
[AAA] => Array
(
[0] => F104_480e9f231b2b5a138f8aa5570ffa8634
)
[ZZZ] => Array
(
[0] => F20_5e742bc21f41a14243c3f72b9fa4815e
)
)
)
The original array is quite large with more keys and values. But everything is in the same structure depicted above.
I'd like to read that in, and return
Array
(
[AAA] => Array
(
[0] => F104_f58f85f9dbbe1ce083ca09a6f9ace679
[1] => F104_480e9f231b2b5a138f8aa5570ffa8634
[2] => F104_d5fde0ad2499052e0eae6dec451f9385
[4] => F104_480e9f231b2b5a138f8aa5570ffa8634
)
[BBB] => Array
(
[0] => F44_e2e052e7b78abbae02ffcf7413302a0c
[1] => F44_4d4da736509babebba7433b203b16753
)
[ZZZ] => Array
(
[0] => F20_5e742bc21f41a14243c3f72b9fa4815e
)
)
What's the least painful and most efficient way of accomplishing this?

Answer 1

Using array_merge_recursive() and array unpacking to pass the separate parts into it...
print_r(array_merge_recursive(...$array));
gives...
Array
(
[AAA] => Array
(
[0] => F104_f58f85f9dbbe1ce083ca09a6f9ace679
[1] => F104_480e9f231b2b5a138f8aa5570ffa8634
[2] => F104_d5fde0ad2499052e0eae6dec451f9385
[3] => F104_480e9f231b2b5a138f8aa5570ffa8634
)
[BBB] => Array
(
[0] => F44_e2e052e7b78abbae02ffcf7413302a0c
[1] => F44_4d4da736509babebba7433b203b16753
)
[ZZZ] => Array
(
[0] => F20_5e742bc21f41a14243c3f72b9fa4815e
)
)

Answer 2

You could use array_map() to traverse the parent array. And use another foreach loop to combine the values. Please note the $output array is passed by reference.
$inputArray = [
0 => [
'AAA' => [
0 => 'F104_f58f85f9dbbe1ce083ca09a6f9ace679',
1 => 'F104_480e9f231b2b5a138f8aa5570ffa8634',
2 => 'F104_d5fde0ad2499052e0eae6dec451f9385',
],
'BBB' => [
0 => 'F44_e2e052e7b78abbae02ffcf7413302a0c',
1 => 'F44_4d4da736509babebba7433b203b16753',
]
],
1 => [
'AAA' => [
0 => 'F104_480e9f231b2b5a138f8aa5570ffa8634'
],
'ZZZ' => [
0 => 'F20_5e742bc21f41a14243c3f72b9fa4815e'
]
]
];
$output = [];
array_map(function($values) use (&$output){
foreach ($values as $key => $value){
if(empty($output[$key])){
$output[$key] = $value;
}else{
$output[$key] = array_merge($output[$key], $value);
}
}
}, $inputArray);
print_r($output);
Here is a working example http://sandbox.onlinephpfunctions.com/code/97909ce93184fad6c33af8eb48d184ae86438774