PHP 数据库树的遍历方法

<?php
session_start();
define ('p_s', path_separator);
define ('root', "./");
set_include_path(root .p_s .'zend' .p_s .root.get_include_path());
//加载zend 框架
require_once root.'zend/loader.php';
require_once 'usercheck.php';//加载访问权限
zend_loader::loadfile('function.class.php', $dirs='class/', $once=false);//加载函数
zend_loader::loadclass('zend_db');//加载数据库类
zend_loader::loadclass('zend_config_ini');//加载配置类
$config = new zend_config_ini('config.php', 'general');//创建配置对象
$db = zend_db::factory($config->db->adapter,$config->db->config->toarray());//创建数据库对象
$select=$db->select();
$select->from('resclass',array('lsh','name'));
$select->where('steps = 1');
$rs=$db->fetchall($select);
foreach ($rs as $res){
echo '    '.$res['lsh'].$res['name']."<br>";
visit($res['lsh'],1);
}
function visit($nodeid,$stept){
global $db;
$recordset = "select lsh,name from resclass where parent=".$nodeid; //搜索nodeid的所有下层节点
$rs=$db->fetchall($recordset);
foreach($rs as $rss){
if(!$rss)
return; //已经是叶子节点，直接返回
else{
for ($i=0;$i<4*$stept;$i++){
echo " ";
}
echo '    '.$rss['lsh'].$rss['name']."<br>";
visit($rss['lsh'],$stept+1);
}
}
}
?>