数据库：
源代码：<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<select>
<?php
$conn=mysql_connect("localhost","root","");
mysql_select_db("dbtest",$conn);
mysql_query("set names utf8");
function wxj($pid,$level){
$sql="select * from folders where pid=$pid";
$result=mysql_query($sql);
while($arr=mysql_fetch_assoc($result)){
echo "<option>";
for($i=0;$i<$level;$i++){
echo " ";
}
echo $arr["f_name"]."</option>";
wxj($arr["id"],$level+1);
}
}
wxj(0,0);
mysql_close();
?>
</select>
</body>
</html>