Return the first level key upon finding a qualifying subarray in a multidimensional array

I have multidimensional array and I need to search for top level key by the value in "add_fields" arrays by "value". I cannot figure out how I can achieve the result.

I tried this code:

array_search(
    '001001',
    array_column(
        array_column(
            $arr,
            "usr_column_504"
        ),
        0
    )
), 

but didn't get anything and I need to get top level key. In this example its **0**;

    array (
        0 => 
            array (
              'id' => 1,
              'group_id' => 327,
              'volume' => 0,
              'vat' => 1,
              'order_id' => 1,
              'add_fields' => 
              array (
                1 => 
                array (
                  'field' => 'usr_column_501',
                  'value' => '',
                ),
                2 => 
                array (
                  'field' => 'usr_column_504',
                  'value' => '001001',
                ),
              ),
            ),
        1 => 
            array (
              'id' => 2,
              'group_id' => 327,
              'vat' => 1,
              'order_id' => 2,
              'add_fields' => 
              array (
                1 => 
                array (
                  'field' => 'usr_column_501',
                  'value' => '',
                ),
                2 => 
                array (
                  'field' => 'usr_column_504',
                  'value' => '001002',
                ),
              ),
            ),
    )

If you want the first key where the value of field equals usr_column_504 you could use an outer and an inner foreach.

When the value of field is found, return the $key from the outer foreach.

foreach ($arr as $key => $item) {  
    foreach ($item["add_fields"] as $addField) {
        if ($addField["field"] === "usr_column_504") {
            echo $key;
            return;
        }
    }
}

Output

0

Php demo