先看一段代码:
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<?php
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class User
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{
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static private $counter = 1;
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public function __construct()
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{
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self::$counter++;
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}
10![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
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static public function getCount()
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{
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return self::$counter;
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}
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public function __destruct()
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{
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self::$counter--;
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}
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}
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echo 'run static getCount:'.User::getCount().'<br>';
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$user1 = new User();
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$user2 = new User();
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echo 'run user1 getCount:'.$user1->getCount().'<br>';
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unset($user1);
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echo 'run user2 getCount:'.$user2->getCount();
29![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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?>
31![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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运行结果:
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run static getCount:1
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run user1 getCount:3
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run user2 getCount:2
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通过如上代码可以得到相关结论:
1、静态变量和静态方法,不需要new一个对象就可以直接使用;
2、当对象被unset后,仍然能够继续使用。
由此可知,静态变量和静态方法,在进程创建的时候就被创建了,而不是在对象创建的时候才被创建,并且其生命周期同该进程的生命周期一样长,其占用的系统资源是初始化进程申请资源的一部分。
至于apache是如何给进程分配内存的,请看下一篇 简单介绍apahce内存管理机制 。
注:每刷新一下页面,就会使服务器端产生一个进程(或线程)处理该请求。