php实现获取某指定叶子结点到根结点的路径

问题：有一个多叉树，如下所示：

    class node {
        public $data = null;
        public $children = null;
        public function __construct($data) {
            $this->data = $data;
        }
    }
    $root = new node(1);
    $child = new node(2);
    $nodeChd = new node(21);
    $nodeChd1 = new node(22);
    $nodeChd2 = new node(23);
    $child->children[]= $nodeChd;
    $child->children[]= $nodeChd1;
    $child->children[]= $nodeChd2;
    $root->children[] = $child;
    $child = new node(3);
    $nodeChd = new node(31);
    $nodeChd1 = new node(32);
    $nodeChd2 = new node(33);
    $child->children[]= $nodeChd;
    $child->children[]= $nodeChd1;
    $child->children[]= $nodeChd2;
    $root->children[] = $child;
    $child = new node(4);
    $root->children[] = $child;
    $child = new node(5);
    $root->children[] = $child;
    $child = new node(6);
    $root->children[] = $child;

要求获取从某指定叶子结点到根结点的路径，使用PHP语言实现。

实现过程如下所示：

function traverseValue($node, $parentPath, $targetValue, &$path, &$flag = false) {
        if (empty($node)) {
            return;
        }

        if ($flag == true) {
            return;
        }

        $temp = $parentPath;
        array_unshift($temp, $node->data);
        $path[$node->data] = $temp;

        if ($targetValue == $node->data) {
            $flag = true;
            return;
        }

        if (empty($node->children)) {
            return;
        }

        foreach ($node->children as $valChildren) {
            traverseValue($valChildren, $temp, $targetValue,$path, $flag);
        }
    }
    
    $pathValue = [];
    $parentPath = [];
    $targetValue = 22;
    $flag = false;
    traverseValue($root, $parentPath, $targetValue,$pathValue, $flag);
    echo "<pre>";
    var_dump($pathValue[$targetValue]);

运行结果如下所示：

array(3) {
  [0]=>
  int(22)
  [1]=>
  int(2)
  [2]=>
  int(1)
}