Filter array with array_walk_recursive but deny specific values

I am trying to filter an array

$array = [
    [
        'id' => 1,
        'some_key' => 'some_value',
        'attribute' => [
            'id' => 45,
            'cat_id' => 1
        ],
        'sub' => [
            'id' => 17,
            'some_key' => 'some_value',
            'attribute' => [
                'id' => 47,
                'cat_id' => 17
            ],
        ],
    ],
    [
        'id' => 2,
        'some_key' => 'some_value',
        'sub' => [
            'id' => 19,
            'some_key' => 'some_value',
        ],
    ]
];

$childArray = [];
array_walk_recursive($array, static function($value, $key) use(&$childArray){
    if($key === 'id') {
        $childArray[] = $value;
    }
});

This returns me an array of all array-fields having id as key.

[1,45,17,47,2,19]

But there is a small problem, some of the array have an key called attribute containing an idkey field that I dont want to have.

[1,17,2,19] //this is what I want

Is there a way to say “don’t take the id inside attribute” ?

My current solution, I added a filter before my filter 😀

/**
 * @param array  $array
 * @param string $unwanted_key
 */
private function recursive_unset(&$array, $unwanted_key)
{
    unset($array[$unwanted_key]);
    foreach ($array as &$value) {
        if (is_array($value)) {
            $this->recursive_unset($value, $unwanted_key);
        }
    }
}

but this seems like this is not the best practice ^^

Answer

You can traverse recursively manually instead of array_walk_recursive and avoid all under attribute key.

<?php

$childArray = [];

function collectIDs($arr,&$childArray){
  foreach($arr as $key => $value){
    if($key === 'attribute') continue;
    if(is_array($value)) collectIDs($value,$childArray);
    else if($key === 'id') $childArray[] = $value;
  }
}

collectIDs($array,$childArray);
print_r($childArray);

Demo: https://3v4l.org/V6uFf