php 树型

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

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

class BinaryTree {
    public $root;

    public function __construct() {
        $this->root = null;
    }

    public function insert($value) {
        if ($this->root === null) {
            $this->root = new TreeNode($value);
        } else {
            $this->insertNode($this->root, $value);
        }
    }

    private function insertNode($node, $value) {
        if ($value < $node->value) {
            if ($node->left === null) {
                $node->left = new TreeNode($value);
            } else {
                $this->insertNode($node->left, $value);
            }
        } else {
            if ($node->right === null) {
                $node->while ($node->right === null) {
                    $node->right = new TreeNode($value);
                } else {
                    $this->insertNode($node->right, $value);
                }
            }
        }
    }

    public function inorderTraversal() {
        $result = [];
        $this->inorder($this->root, $result);
        return $result;
    }

    private function inorder($node, &$result) {
        if ($node !== null) {
            $this->inorder($node->left, $result);
            $result[] = $node->value;
            $this->inorder($node->right, $result);
        }
    }
}

// 使用示例
$tree = new BinaryTree();
$tree->insert(5);
$tree->insert(3);
$tree->insert(7);
$tree->insert(2);
$tree->insert(4);
$tree->insert(6);
$tree->insert(8);

print_r($tree->inorderTraversal()); // 输出: Array ( [0] => 2 [1] => 3 [2] => 4 [3] => 5 [4] => 6 [5] => 7 [6] => 8 )