类和变量放入Session的差别

[iamyuqing]

刚开始研究OOP，发现一个问题，不知道哪里可以求证到原理
比如下面的代码，定义一个cart类$cart，并将其放入$_SESSION['cart']中，当$cart发生变动时，$_SESSION['cart']也随之变动，但是如果把变量$str放入$_SESSION['str']时，$str的变动就不影响$_SESSION['str']了。

在PHP手册里面没找到关于这个差别的说明，哪位老大知道PHP是以什么样的机制来处理自定义类和变量在SESSION中的存储么？谢谢！

<?php
session_start();
class cart{
	var $items;
	var $total;
	var $sum;

	function add_item($id,$num,$price){
		$this->items[$id]+=$num;
		$this->total+=$num*$price;
		$this->sum+=$num;
	}

	function remove_item($id,$num,$price){
		$this->items[$id]-=$num;
		$this->total-=$num*$price;
		$this->sum-=$num;
	}

	function view_items(){
		$rs=$this->items;
		$keys=array_keys($rs);
		print "<table border=1><caption>Item List</caption><tr align=center><td>Item</td><td>Number</td><td>remark</td></tr>";
		foreach($keys as $key){
			print "<tr><td>".$key."</td><td>".$rs[$key]."</td><td>-</td></tr>";}
		print "<tr><td colspan=3>Total：".$this->total."</td></tr></table>";}
	}
/*
$cart=new cart;
$cart->add_item("cake",10,25);
$cart->add_item("candy",10,15);
$cart->add_item("apple",10,25);
$cart->add_item("orange",10,25);
$cart->add_item("wine",10,25);
$_SESSION['cart']=$cart;
$cart->view_items();
$cart->remove_item("bay",5,25);
$cart->remove_item("apple",5,3);
$cart->view_items();
*/
print "sum from session:".$_SESSION['cart']->sum."<br>";
print_r($_SESSION['cart']);
$str="aaa";
$_SESSION['str']=$str;
$str="bbb";
print $_SESSION['str'];

?>

[jlzan1314]

php5 以上是引用传递类的.变量不是引用传递的.

[iamyuqing]

[Quote=引用 1 楼 jlzan1314 的回复:]
php5 以上是引用传递类的.变量不是引用传递的.
[/Quote]

谢谢！那么如果要引用传递类，让类作为变量保存时处于静态，有什么办法么？

[CunningBoy]

$cart = new cart; //这里的$cart是一个reference
$str是变量。

$_SESSION['cart'] = $cart; //这个是让$_SESSION['cart']和$cart指向同一块数据。
$_SEESION['str' = $str; //是两个变量；

具体可以参看PHP手册“Classes and Objects (PHP 5)”部分。

[jlzan1314]

<?php
session_start();
class cart{
    var $items;
    var $total;
    var $sum;

    function add_item($id,$num,$price){
        $this->items[$id]+=$num;
        $this->total+=$num*$price;
        $this->sum+=$num;
    }

    function remove_item($id,$num,$price){
        $this->items[$id]-=$num;
        $this->total-=$num*$price;
        $this->sum-=$num;
    }

    function view_items(){
        $rs=$this->items;
        $keys=array_keys($rs);
        print "<table border=1><caption>Item List</caption><tr align=center><td>Item</td><td>Number</td><td>remark</td></tr>";
        foreach($keys as $key){
            print "<tr><td>".$key."</td><td>".$rs[$key]."</td><td>-</td></tr>";}
        print "<tr><td colspan=3>Total：".$this->total."</td></tr></table>";}
    }

$cart=new cart;
$cart->add_item("cake",10,25);
$cart->add_item("candy",10,15);
$cart->add_item("apple",10,25);
$cart->add_item("orange",10,25);
$cart->add_item("wine",10,25);
$_SESSION['cart']=clone $cart;
#$_SESSION['cart']=$cart;
$cart->remove_item("bay",5,25);
$cart->remove_item("apple",5,3);

$_SESSION['cart']->view_items();
$cart->view_items();

print "sum from session:".$_SESSION['cart']->sum."<br>";
print_r($_SESSION['cart']);
$str="aaa";
$_SESSION['str']=$str;
$str="bbb";
print $_SESSION['str'];

?>

注意clone 的用法.