php 简单的实现无限级分类树

php
数据表

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$sql = "select id,class_cid,class_name from hl_goods_class order by id asc ";
$items = $this->fetch_list($sql);

        for($i=1;$i<=count($items);$i++){
            $aa[$i] = $items[$i-1];
        }
        $tree = array();
        foreach ($aa as $item) {
            if (isset($aa[$item['class_cid']])) {

                $aa[$item['class_cid']]['son'][] = &$aa[$item['id']];
            } else {
                $tree[] = &$aa[$item['id']];
            }
        }
        return $tree;