使用php递归函数获取二叉树中的级别

class TreeNode {
    public $value;
    public $left;
    public $right;

    public function __construct($value) {
        $this->value = $value;
        $this->left = null;
        $this->right = null;
    }
}

function getLevel($node, $level) {
    if ($node == null) {
        return;
    }

    echo "节点值：" . $node->value . "，级别：" . $level . "<br>";

    getLevel($node->left, $level + 1);
    getLevel($node->right, $level + 1);
}

// 创建二叉树
$root = new TreeNode(1);
$root->left = new TreeNode(2);
$root->right = new TreeNode(3);
$root->left->left = new TreeNode(4);
$root->left->right = new TreeNode(5);
$root->right->left = new TreeNode(6);
$root->right->right = new TreeNode(7);

// 调用递归函数获取节点级别
getLevel($root, 1);