Merge two json overwriting different innested objects in php

I have two json objects with innested objects and I need to merge them into one object overwriting the original values with the ones from the second object.

First JSON

{
   "field 1" : {
      "key 1": "value 1",
      "key 2": {
         "subkey 1": "subvalue 1",
         "subkey 2": "subvalue 2"
      },
      "key 3": "value 3"
   },
   "field 2": {
      "key 4": "value 4",
      "key 5": "value 5"
   },
   "field 3": {
      "key6": "value 6"
   }
}

Second JSON, contains only the fields that have values that differs from the first JSON

{
   "field 1" : {
      "key 1": "value 10",
      "key 2": {
         "subkey 2": "subvalue 20"
      }
   },
   "field 2": {
      "key 4": "value 40"
   }
}

Expected result, the first JSON with the values modified of the second JSON

{
   "field 1" : {
      "key 1": "value 10",
      "key 2": {
         "subkey 1": "subvalue 1",
         "subkey 2": "subvalue 20"
      },
      "key 3": "value 3"
   },
   "field 2": {
      "key 4": "value 40",
      "key 5": "value 5"
   },
   "field 3": {
      "key6": "value 6"
   }
}

I already tried with array_merge but when it finds the same key in both objects replace the value of the first with the value of the second. In this case the result is field 1 and field 2 from the second JSON and field 3 from the first.

Array_merge_recursive instead adds the second values to the first ones so that, for example, for "key 1" the values becomes

"[value 1, value 10]"

Any help?

Ps. In this example I used JSON objects with only two levels but there could be more

Solution

I think that you want array replace instead of merge.

<?php
$j1 = '{
   "field 1" : {
      "key 1": "value 1",
      "key 2": {
         "subkey 1": "subvalue 1",
         "subkey 2": "subvalue 2"
      },
      "key 3": "value 3"
   },
   "field 2": {
      "key 4": "value 4",
      "key 5": "value 5"
   },
   "field 3": {
      "key6": "value 6"
   }
}';

$j2 = '{
    "field 1" : {
       "key 1": "value 10",
       "key 2": {
          "subkey 2": "subvalue 20"
       }
    },
    "field 2": {
       "key 4": "value 40"
    }
 }';

$a1 = json_decode($j1, true);

$a2 = json_decode($j2, true);


$a = array_replace_recursive($a1, $a2);
print_r( json_encode($a, JSON_PRETTY_PRINT));
?>

The output

{
    "field 1": {
        "key 1": "value 10",
        "key 2": {
            "subkey 1": "subvalue 1",
            "subkey 2": "subvalue 20"
        },
        "key 3": "value 3"
    },
    "field 2": {
        "key 4": "value 40",
        "key 5": "value 5"
    },
    "field 3": {
        "key6": "value 6"
    }
}

Check https://www.php.net/manual/en/function.array-replace-recursive