phpcms怎么调用三级栏目

<?php
// 假设我们有一个函数 get_sub_categories 用于获取子栏目
function get_sub_categories($parent_id) {
    $sql = "SELECT * FROM v9_category WHERE parentid = $parent_id";
    $query = pc_base::load_model('category_model')->query($sql);
    $categories = array();
    foreach ($query as $row) {
        $categories[] = $row;
        $categories = array_merge($categories, get_sub_categories($row['catid'])); // 递归获取子栏目
    }
    return $categories;
}

// 获取顶级栏目
$top_categories = pc_base::load_model('category_model')->select("parentid=0");

foreach ($top_categories as $top_category) {
    echo "顶级栏目: " . $top_category['catname'] . "<br>";
    $second_categories = get_sub_categories($top_category['catid']);
    foreach ($second_categories as $second_category) {
        echo "  二级栏目: " . $second_category['catname'] . "<br>";
        $third_categories = get_sub_categories($second_category['catid']);
        foreach ($third_categories as $third_category) {
            echo "    三级栏目: " . $third_category['catname'] . "<br>";
        }
    }
}
?>