新手上路，多多关照

class Employee
{
var $empno; // 员工人数
var $empnm; // 员工姓名
function add_employee($in_num, $in_name)
{
$this->empno = $in_num;
$this->empnm = $in_name;
}
function show()
{
echo "$this->empno, $this->empnm";
return;
}
function changenm($in_name)
{
$this->empnm = $in_name;
}
}
$sbabu = new Employee;
$sbabu->add_employee(10,"sbabu");
$sbabu->changenm("babu");
$sbabu->show();


输出是什么啊？程序有错误吗？