php 无限级 SelectTree 类

/* 
author: nick 
date: 2009.05.17 
功能：生成SeletTree 
属性: 
$result 结果集 
$id_field 自身id字段 
$parent_field 父类id字段 
$option_text 选项显示名称 
$select_name 下拉菜单的名称 
$elected 默认选中 
$no_top 是否需要顶层选项 
$level 层深度 
$parent_id 同层中的id 
*/ 
class SelectTree{ 
public $result; 
public $select_name; 
public $option_text; 
public $elected; 
public $id_field; 
public $parent_field; 
public $no_top; 
public $level; 
public $parent_id; 
public $getarray; 
function __construct($result,$id_field,$parent_field,$option_text,$select_name='',$elected=0,$no_top=0,$level=0,$parent_id=0){ 
$this->result =$result; 
$this->id_field =$id_field; 
$this->parent_field =$parent_field; 
$this->option_text =$option_text; 
$this->select_name =$select_name; 
$this->elected =$elected; 
$this->no_top =$no_top; 
$this->level =$level; 
$this->parent_id =$parent_id; 
$this->getarray =self::getArray(); 
} 
/* 
功能：返回Tree二维数组 
*/ 
function getArray(){ 
$arrays=array(); 
while($row=mysql_fetch_array($this->result)){ 
$arrays[$row[$this->parent_field]][$row[$this->id_field]]=$row; 
} 
return $arrays; 
} 
/* 
功能：获取SelectTree 
*/ 
function getSelectTree(){ 
$tree = '<select name="'.$this->select_name.'">'; 
if($no_top){ 
$tree .= '<option value="0">最顶层</option>'; 
} 
self::buildTree($this->getarray,&$tree,$this->id_field,$this->option_text,$this->selected,$this->level,$this->parent_id); //生成树状结构 
$tree .= '</select>'; 
return $tree; 
} 
/* 
功能：递归构建树状结构 
*/ 
function buildTree($array,&$tree,$option_value,$option_text,$selected,$level=0,$parent_id=0){ 
if(is_array($array[$parent_id])){ 
for($i=0;$i<$level;$i++) 
$space .= ' '; //选项缩进深度 
foreach($array[$parent_id] as $key => $value){ 
if($value[$option_value] == $selected){ 
$tree .= '<option value="'.$value[$option_value].'" selected="selected">'.$space.$value[$option_text]."</option>"; 
}else{ 
$tree .= '<option value="'.$value[$option_value].'">'.$space.$value[$option_text]."</option>"; 
} 
$tree .=self::buildTree($array,&$tree,$option_value,$option_text,$selected,$level+1,$key); 
} 
}else{ 
$tree .= ''; 
} 
} 
} 
/****************************************************************************/ 
header("CONTENT-TYPE:TEXT/HTML;CHARSET=UTF-8"); 
mysql_connect("localhost","root","root"); 
mysql_select_db("tree"); 
mysql_query('set names utf8'); 
$result = mysql_query("select * from tvmenu"); 
$tree=new SelectTree($result,'id','bid','name','tree'); 
echo $tree->getSelectTree();