array_select

array_select.php

<?php

function array_select(array $array, array $filter): array
{
    return array_map(function (array $object) use ($filter) {
        $object = array_intersect_key($object, $filter);
        
        foreach ($object as $key => $value) {
            if (is_array($filter[$key])) {
                $object[$key] = array_select($object[$key], $filter[$key]);
            }
        }
        
        return $object;
    }, $array);
}

$array = json_decode('[
  {
    "_id": "5cf685bd902ff4cb44382c9c",
    "index": 0,
    "friends": [
      {
        "id": 0,
        "name": "Sandoval Salas"
      },
      {
        "id": 1,
        "name": "Potter Gross"
      }
    ]
  }
]', true);

$result = array_select($array, [
    'index' => true, 
    'friends' => ['id' => true],
]);

print_r($result);

/*
Output for 7.1.25 - 7.3.6
    Array
    (
        [0] => Array
            (
                [index] => 0
                [friends] => Array
                    (
                        [0] => Array
                            (
                                [id] => 0
                            )

                        [1] => Array
                            (
                                [id] => 1
                            )

                    )

            )

    )
*/