반복적 접근 방식을 사용하여 다차원 배열을 XML로 변환하려면 어떻게 해야 합니까?

<code class="php">class TranformArrayIterator extends RecursiveIteratorIterator
{
    // Custom functionality for outputting indentation, XML tags, etc.
}</code>

<code class="php">$nodes = ...;
$iterator = new TranformArrayIterator(new RecursiveArrayIterator($nodes));</code>

<code class="php">foreach ($iterator as $val) {
    echo $val;
}</code>

<code class="xml"><nodes>
    <node>parent node</node>
    <node>parent node</node>
    <nodes>
        <node>child node</node>
        <node>child node</node>
        <nodes>
            <node>grand child node</node>
            <node>grand child node</node>
        </nodes>
    </nodes>
</nodes></code>