php ul分级分类

<?php
// 假设这是从数据库中获取的分类数据
$categories = [
    ['id' => 1, 'name' => '电子产品', 'parent_id' => 0],
    ['id' => 2, 'name' => '手机', 'parent_id' => 1],
    ['id' => 3, 'name' => '小米', 'parent_id' => 2],
    ['id' => 4, 'name' => '苹果', 'parent_id' => 2],
    ['id' => 5, 'name' => '书籍', 'parent_id' => 0],
];

// 递归函数生成UL分级分类
function generateUl($categories, $parent_id = 0, $level = 0)
{
    $html = '';
    foreach ($categories as $category) {
        if ($category['parent_id'] == $parent_id) {
            $html .= '<li style="margin-left: ' . ($level * 20) . 'px;">' . $category['name'];
            $html .= generateUl($categories, $category['id'], $level + 1);
            $html .= '</li>';
        }
    }
    return '<ul>' . $html . '</ul>';
}

echo generateUl($categories);
?>