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背景：处理网站访问时后面才进行写日志，常看到类似的类里在单例中这样使，好多都是说类中，而没有谈到类中是单例的使用方法，如下：
   public static function instance($group ='default')     {         if (!isset(self::$_instance[$group]) ||self::$_instance[$group] === NULL) {             // Create a new instance             self::$_instance[$group] = new self($group);             // Write the logs at shutdown             register_shutdown_function(array(self::$_instance[$group], 'write'));         }         return self::$_instance[$group];     }

简单实践：
     <?php     class TestShutdownLog {        private $running;        public function main() {            $this->running = true;            ob_start();            error_reporting(E_ALL);            register_shutdown_function(array($this, "clean_exit"));            echo "注册完shutdown函数\n";            // triggers E_ERROR            $this->running = false;        }        public function clean_exit() {                echo "clean_exit时写在web运行完后在这儿做写日志等的操作,单例模式注册日志先放前面数组，后面在这儿写。";        }     }     ?> <?php class webStartAndEnd{     function TestShutDown()     {         $t = new TestShutdownLog();         $t->main();//该类注册shutdown函数     }     function dbOrData(){         echo "做数据链接，写入日志内容但不写在shutdown：clean_exit时写。\n";     }     function TestAfter(){//做完所有扫尾事宜        $f = new testafter();        $f->after();     } } ?> <?php class testafter{     function after()     {         echo "干完所有事情了，立即退出\n";     } } ?> <?php $shutDownTest = new webStartAndEnd(); $shutDownTest ->TestShutDown(); $shutDownTest ->dbOrData(); $shutDownTest ->TestAfter(); ?>

运行情况：
---------- 调试PHP ----------
注册完shutdown函数
做数据链接，写入日志内容但不写在shutdown：clean_exit时写。
干完所有事情了，立即退出
clean_exit时写在web运行完后在这儿做写日志等的操作,单例模式注册日志先放前面数组，后面在这儿写。
输出完成 (耗时 0 秒) - 正常终止

函数讲解：
PHP提供register_shutdown_function()这个函数，能够在脚本终止前回调注册的函数
register_shutdown_function例子代码:
<?php function Test() {      if(!file_exists('Test.txt')){     //判断如果文件不存在!! echo '文件不存在,我要创建一个:';         $Str = fopen('Test.txt',"w+");               fwrite($Str,'you are write after exit');         fclose($Str); echo "创建完成!"; }else {                           //如果存在;         echo '文件已经存在'; } } register_shutdown_function('Test'); for($i=0;$i<10;$i++){ echo "Echo<br/>"; } exit; ?>
There is a note "Shutdown function is called during the script shutdown so headers are always already sent.", but my php 5.1 seems to act differently.
Example:
<?php class Test {    private $running;    public function main() {        $this->running = true;        ob_start();        error_reporting(E_ALL);        register_shutdown_function(array($this, "clean_exit"));        echo "Hello";        // triggers E_ERROR        $fatal->error();        $this->running = false;      }    public function clean_exit() {        if ($this->running) {            header("Location: error.php");          }      } } $t = new Test(); $t->main(); ?>
This example redirects you on error.php, this could be a simple way to handle E_ERROR.

来自：http://314200716.blog.163.com/blog/static/55358027201051241028808/
更多兼容参考：
http://www.laruence.com/2008/09/04/498.html

作者：jackxiang@向东博客 专注WEB应用 构架之美 --- 构架之美，在于尽态极妍 | 应用之美，在于药到病除
地址：https://jackxiang.com/post/6784/
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