$this->dao=& $dao;
是怎么回事呀 &$ 是传地址吗。传了后两个变量地址一下？
可是他们本身是一个变量呀

[PHP]
<?php
/**
* Fetches "products" from the database
*/
class ProductModel {
/**
* Private
* $dao an instance of the DataAccess class
*/
var $dao;

//! A constructor.
/**
* Constucts a new ProductModel object
* @param $dbobject an instance of the DataAccess class
*/
function ProductModel (&$dao) {
$this->dao=& $dao;
}
.
.
.

[/PHP]