PHP如何迭代层次化平面数组？

function iterateArray($array, $prefix = '') {
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            iterateArray($value, $prefix . $key . '.');
        } else {
            echo $prefix . $key . ': ' . $value . '<br>';
        }
    }
}

$array = array(
    'name' => 'John',
    'age' => 30,
    'address' => array(
        'street' => '123 Main St',
        'city' => 'New York',
        'country' => 'USA'
    )
);

iterateArray($array);

name: John
age: 30
address.street: 123 Main St
address.city: New York
address.country: USA