合并多维数组PHP而不更改键

$array1 = array(
    "key1" => array(
        "subkey1" => "value1",
        "subkey2" => "value2"
    ),
    "key2" => array(
        "subkey3" => "value3",
        "subkey4" => "value4"
    )
);

$array2 = array(
    "key1" => array(
        "subkey2" => "new value",
        "subkey5" => "value5"
    ),
    "key3" => array(
        "subkey6" => "value6"
    )
);

$result = array_merge_recursive($array1, $array2);

print_r($result);

Array
(
    [key1] => Array
        (
            [subkey1] => value1
            [subkey2] => Array
                (
                    [0] => value2
                    [1] => new value
                )
            [subkey5] => value5
        )
    [key2] => Array
        (
            [subkey3] => value3
            [subkey4] => value4
        )
    [key3] => Array
        (
            [subkey6] => value6
        )
)