php带有数据库的二级联动菜单

class myconn{

var $conn;
var $result;

function myconn(){
   $this->conn=mysql_connect('localhost','root','1234');
   mysql_select_db('allin',$this->conn);
}

function process($sql){
   mysql_query('set names gbk');
   $result=mysql_query($sql);
   return $result;
}

}

?>

请选择

$conn=new myconn();
$sql="select * from topclass where parentid=0";
$result=$conn->process($sql);
while($data=mysql_fetch_array($result))
{
?>

   }

?>

请选择