php mysql无限分类排序

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询数据
$sql = "SELECT id, name, parent_id FROM categories ORDER BY path";
$result = $conn->query($sql);

// 处理数据
$categories = [];
while ($row = $result->fetch_assoc()) {
    $row['children'] = [];
    $categories[$row['id']] = $row;
}

foreach ($categories as $id => $category) {
    if ($category['parent_id'] != 0) {
        $categories[$category['parent_id']]['children'][] = &$categories[$id];
    }
}

// 输出结果
function print_categories($categories, $level = 0) {
    foreach ($categories as $category) {
        echo str_repeat("  ", $level) . $category['name'] . "\n";
        if (!empty($category['children'])) {
            print_categories($category['children'], $level + 1);
        }
    }
}

print_categories(array_values($categories));

$conn->close();
?>