PHP - Merge append multiple json arrays - php

Question

I need to merge/join multiple json string that contains arrays (which also need to be merged) but I don't know what is the best way to achieve this :
Initial array of json strings (called $rrDatas in my example below):
Array
(
[0] => {"asset":[1],"person":[1]}
[1] => {"asset":[2]}
)
Expected result :
{"asset":[1,2],"person":[1]}
The main difficulty is that the number of arrays is undefined (my example is made with 2 arrays but it could be 3,4 etc.). The second difficulty is that there can be multiple properties (like "asset", "person" etc. however always arrays). These possible properties are known but are many so it would be better if the algorithm is dynamic.
What I am able to do at the moment :
$mergedAssets['asset'] = [];
foreach ($rrDatas as $rrData)
{
$rrDataJson = \GuzzleHttp\json_decode($rrData, true);
$mergedAssets['asset'] = array_merge($mergedAssets['asset'],$rrDataJson['asset']);
}
$result = \GuzzleHttp\json_encode($mergedAssets, true);
Result :
{"asset":[1,2]}
This works well but this is not dynamic, should I duplicate this part for each possible properties (i.e. "person", etc.) ?
Thanks,
Guillaume
Edit : Brett Gregson's and krylov123's answers below helped me build my own solution which is a mix between both suggestion:
$mergedJson = [];
foreach ($rrDatas as $rrData)
{
$rrDataJson = \GuzzleHttp\json_decode($rrData, true);
foreach(array_keys($rrDataJson) as $property)
{
$mergedJson[$property] = array_merge($mergedJson[$property] ?? [], $rrDataJson[$property]);
}
}
return \GuzzleHttp\json_encode($mergedJson, true);
Find below a better example :
$rrDatas = Array (
[0] => {"asset":[1,2],"person":[1],"passive":[1]}
[1] => {"asset":[3],"charge":[1],"passive":[2]}
)
Which must result in :
{"asset":[1,2,3],"person":[1],"passive":[1,2],"charge":[1]}
Edit 2 : I have just tried Progrock's solution and it seems to work perfectly as well : https://3v4l.org/7hSqi

Answer 1

You can use something like:
$output = []; // Prepare empty output
foreach($rrDatas as $inner){
foreach($inner as $key => $value){
$output[$key][] = $value;
}
}
echo json_encode($output); // {"asset":[1,2],"person":[1]}
Which should give you the desired output. This should work regardless of the keys within the individual arrays and even with empty arrays.
Working example here
Another example with more arrays and more keys and empty arrays

Answer 2

<?php
$array =
[
'{"asset":[1],"person":[1]}',
'{"asset":[2]}',
];
$array = array_map(function($v) { return json_decode($v, true);}, $array);
$merged = array_merge_recursive(...$array);
print json_encode($merged);
Output:
{"asset":[1,2],"person":[1]}

Answer 3

You need to use foreach ($array as $key => $value) iteration, to be able to dynamicaly use keys of your json array (e.g. "asset" and "person").
Solution:
$mergedAssets['asset'] = [];
foreach ($rrDatas as $key => $value)
{
$rrDataJson = \GuzzleHttp\json_decode($value, true);
$mergedAssets[$key] = array_merge($mergedAssets[$key],$rrDataJson[$key]);
}
$result = \GuzzleHttp\json_encode($mergedAssets, true);