php无限归类

php无限分类
db设计：

CREATE TABLE IF NOT EXISTS `test` (`id` INT(1) NOT NULL AUTO_INCREMENT,`path` VARCHAR(255) NOT NULL,`name` VARCHAR(255) NOT NULL,PRIMARY KEY (`id`))ENGINE = MYISAM DEFAULT CHAR SET ='utf8';INSERT INTO `test` VALUES ('', '0', '公司'),('', '0-1', '部门一'),('', '0-2', '部门二'),('', '0-3', '部门三'),('', '0-1-1', '小组一'),('', '0-1-2', '小组二'),('', '0-2-1', '小组三'),('', '0-2-2', '小组四');

<?php$db = mysql_connect('localhost', 'root', 'zhw') or die('could not conenct to db');mysql_query("SET charset 'utf8'");mysql_select_db('test', $db);$query = mysql_query("SELECT `id`, concat(`path`, '-', id) AS pwd, `name` FROM `test` ORDER BY `pwd`");while ($row = mysql_fetch_array($query)){$indent = str_repeat('&nbsp;&nbsp;&nbsp;&nbsp;', count(explode('-', $row['pwd'])) - 2);$option .= "<option value='{$row['id']}'>{$indent}{$row['name']}</option>";}echo "<select>{$option}</select>";