原理: pid = 0 的字段为顶级分类, 次级分类的 pid 则为上一级分类的 id, 以此类推来实现无限极分类

无限极分类建表

CREATE TABLE category (

　　`id` INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,

　　`name` VARCHAR(32) NOT NULL DEFAULT '',

　　`pid` INT(5) NOT NULL,

　　......

)Engine=InnoDB DEFAULT CHARSET='utf8';

 

public function tree($data, $parentid = 0, $space = 0) {

        $tree = [];

// 字符串重复的次数

        $space += 1;

        if (!empty($data)) {

            foreach ($data as $key => $value) {

                if ($value['parentid'] == $parentid) {

                    if ($value['parentid'] != 0) {

                        $value['title'] = str_repeat("—", $space) . $value['title'];

                    }

                    $tree[] = $value;

　　　　　　// 将父id为0的数据的id作为参数实现递归

                    $tree = array_merge($tree, $this->tree($data, $value['id'], $space));

                }

            }

        }

        return $tree;

    }

　// 处理已获得的数据

    public function listDown($data) {

        $list = [0 => '————请选择————'];

        if (!empty($data)) {

            foreach ($data as $key => $value) {

                $list[$value["id"]] = $value['title'];

            }

        }

        return $list;

    }