register_shutdown_function

(PHP 4, PHP 5, PHP 7, PHP 8)

register_shutdown_function — 注册一个会在php中止时执行的函数

说明

register_shutdown_function ( callable $callback , mixed $parameter = ? , mixed $... = ? ) : void

注册一个 callback ，它会在脚本执行完成或者 exit() 后被调用。

可以多次调用 register_shutdown_function() ，这些被注册的回调会按照他们注册时的顺序被依次调用。 如果你在注册的方法内部调用 exit()， 那么所有处理会被中止，并且其他注册的中止回调也不会再被调用。

参数

callback

待注册的中止回调

中止回调是作为请求的一部分被执行的，因此可以在它们中进行输出或者读取输出缓冲区。

parameter

可以通过传入额外的参数来将参数传给中止函数

...

返回值

没有返回值。

错误／异常

如果传入的callback不是可调用的，那么将会产生一个 E_WARNING 级别的错误。

范例

Example #1 register_shutdown_function() 例子

<?php
function shutdown()
{
    // This is our shutdown function, in 
    // here we can do any last operations
    // before the script is complete.

    echo 'Script executed with success', PHP_EOL;
}

register_shutdown_function('shutdown');
?>

注释

Note:

在某些web server（如Apache）上，可以在中止函数内对脚本的工作目录进行修改。

Note:

如果进程被信号SIGTERM或SIGKILL杀死，那么中止函数将不会被调用。尽管你无法中断SIGKILL，但你可以通过pcntl_signal() 来捕获SIGTERM，通过在其中调用exit()来进行一个正常的中止。

参见

User Contributed Notes

ohcc at 163 dot com 09-Jun-2020 04:06
As of PHP 7.4, an exception thrown within the user-defined shutdown function can be caught by the user-defined exception handler.

<?php
    set_error_handler(
        function($level, $error, $file, $line){
            if(0 === error_reporting()){
                return false;
            }
            throw new ErrorException($error, -1, $level, $file, $line);
        },
        E_ALL
    );

    register_shutdown_function(function(){
        $error = error_get_last();
        if($error){
            throw new ErrorException($error['message'], -1, $error['type'], $error['file'], $error['line']);
        }
    });

    set_exception_handler(function($exception){
        // ... more code ...
    });   
   
    require 'NotExists.php';
Anonymous 16-Mar-2019 10:08
warning: in addition to SIGTERM and SIGKILL, the shutdown functions won't run in response to SIGINT either. (observed on php 7.1.16 on windows 7 SP1 x64 + cygwin  and php 7.2.15 on Ubuntu 18.04)
marcelotpcruz at gmail dot com 28-Nov-2018 09:58
I elaborated following functions, so you can close your connection if you can't count on fastcgi_finish_request.

You'll use puts instead of echo, so you can close the connection whenever you want as long as you don't touch echo when you use those functions.
It works it compression and is easy to adapt:

function connsettings($name, $val=null){
    static $settings = array();
   
    if(!isset($settings[$name]))
        $settings[$name] = false;
    if($val !== null)
        $settings[$name] = $val;
   
    return $settings[$name];
};//Just saving compression and init var to check if it's true or false

function puts(){
//Using args so it works like echo with comma ands dots
    $numargs = func_num_args();
    $arg_list = func_get_args();
    $string = '';
   
    if($numargs === 0)
        return;
    else if($numargs > 1)
        for($i = 0; $i < $numargs; $i++)
            $string .= $arg_list[$i];
    else
        $string = $arg_list[0];

    if(connsettings('init') === false)
    {
        // buffer all upcoming output - make sure we care about compression:
        if(ob_start("ob_gzhandler"))
            connsettings('compression', true);
        else
            ob_start();

        connsettings('init', true);
        register_shutdown_function('puts', null, true);
    }
    echo $string;
}
function close(){
    if(!headers_sent())//it may work without this verification when no compression but may lead to uncomplete data
    {
        // send headers to tell the browser to close the connection
        ob_end_flush(); // Order here matter, it won't work if it goes after Content-Length
        if(connsettings('compression') === false)
            header("Content-Encoding: none");
        header('Content-Length: ' . ob_get_length());
        header('Connection: close');   
        // flush all output
        //ob_end_flush();
        ob_flush();
        flush();
        // close current session
        if (session_id()) session_write_close();
        set_time_limit(0);
        ignore_user_abort(true);
    }
}
raat1979 at gmail dot com 08-Feb-2017 07:31
I wanted to set the exit code for a CLI application from a shutdown function by using a class property,

Unfortunataly (as per manual)  "If you call exit() within one registered shutdown function, processing will stop completely and no other registered shutdown functions will be called." 

As a result if I call exit in my shutdown function I will break other shutdown functions (like one that logs fatal errors to syslog) 

However! (as per manual)  "Multiple calls to register_shutdown_function() can be made, and each will be called in the same order as they were registered."

As luck would have it you are also able to register a shutdown function from within a shutdown function (at least in PHP 7.0.15 and 5.6.30)

in other words if you register a shutdown function inside a shutdown function it is appended to the shutdown function queue.

<?php
class SomeApplication{
    private $exitCode = null;
       
    public function __construct(){
        register_shutdown_function(function(){
        echo "some registered shutdown function";
            register_shutdown_function(function(){
                echo "last registered shutdown function";
                // one might even consider another register shutdown_function if one expects other shutdown functions to do the same... 
                exit($this->exitCode === null ? 0 : $this->exitCode);
            });
        });
    }
}
?>
xcl_rockman at qq dot com 25-Sep-2015 06:02
for static call
register_shutdown_function(function () {
                demo::shutdownFunc();
});
m dot agkopian at gmail dot com 30-Apr-2014 10:29
Use this small snippet inside your bootstrap in order to always have a way to know reliably what was the last page of your site that the user have visited, without having to use $_SERVER['HTTP_REFERER'].

<?php
session_start();

// Get current page
$current_page = htmlspecialchars($_SERVER['SCRIPT_NAME'], ENT_QUOTES, 'UTF-8');
$current_page .= $_SERVER['QUERY_STRING'] ? '?'.htmlspecialchars($_SERVER['QUERY_STRING'], ENT_QUOTES, 'UTF-8') : '';

// Set previous page at the end
register_shutdown_function(function ($current_page) {
    $_SESSION['previous_page'] = $current_page;
}, $current_page);
?>
Tim 01-Nov-2013 04:35
register_shutdown_function seems to be immune to whatever value was set with set_time_limit or the max_execution_time value defined in php.ini.
<?php
function asdf() {
    echo microtime(true) . '<br>';
    sleep(1);
    echo microtime(true) . '<br>';
    sleep(1);
    echo microtime(true) . '<br>';
}
register_shutdown_function('asdf');
set_time_limit(1);

while(true) {}
?>
The output is three lines.
matteosistisette at gmail dot com 13-Apr-2013 05:42
In PHP 5.1.6 things don't work as described here.

The truth is that connection_status() just always returns 0 whether or not the client has aborted (e.g. the user hit the stop button), and that (consistently with this) the registered shutdown function will only be called on exit, but NOT when the connection is aborted from the user.

That is, PHP does NOT detect when the connection is aborted.
alexyam at live dot com 08-Apr-2012 03:50
When using php-fpm, fastcgi_finish_request() should be used instead of register_shutdown_function() and exit()

For example, under nginx and php-fpm 5.3+, this will make browsers wait 10 seconds to show output:

<?php
    echo "You have to wait 10 seconds to see this.<br>";
    register_shutdown_function('shutdown');
    exit;
    function shutdown(){
        sleep(10);
        echo "Because exit() doesn't terminate php-fpm calls immediately.<br>";
    }
?>

This doesn't:

<?php
    echo "You can see this from the browser immediately.<br>";
    fastcgi_finish_request();
    sleep(10);
    echo "You can't see this form the browser.";
?>
david dot schueler at tel-billig dot de 11-Nov-2010 04:51
I had a problem when forking a child process and accessing the variables by using the "global" keyword in the shutdown function.
So i used another way for getting the variables to the shutdown function: I passed them by reference.

Example:
<?php
function shutdown_function (&$test) {
    echo __FUNCTION__.'(): $test = '.$test."\n";
}

$test = 1;
register_shutdown_function('shutdown_function', &$test);
echo '$test = '.$test."\n";

// do some stuff and change the variable values
$test = 2;

// now the shutdown function gets called
exit(0);
?>

Maybe tis helps someone. (I'm using PHP 5.2.11)
emanueledelgrande ad email dot it 19-Sep-2010 07:53
A lot of useful services may be delegated to this useful trigger.
It is very effective because it is executed at the end of the script but before any object destruction, so all instantiations are still alive.

Here's a simple shutdown events manager class which allows to manage either functions or static/dynamic methods, with an indefinite number of arguments without using any reflection, availing on a internal handling through func_get_args() and call_user_func_array() specific functions:

<?php
// managing the shutdown callback events:
class shutdownScheduler {
    private $callbacks; // array to store user callbacks
   
    public function __construct() {
        $this->callbacks = array();
        register_shutdown_function(array($this, 'callRegisteredShutdown'));
    }
    public function registerShutdownEvent() {
        $callback = func_get_args();
       
        if (empty($callback)) {
            trigger_error('No callback passed to '.__FUNCTION__.' method', E_USER_ERROR);
            return false;
        }
        if (!is_callable($callback[0])) {
            trigger_error('Invalid callback passed to the '.__FUNCTION__.' method', E_USER_ERROR);
            return false;
        }
        $this->callbacks[] = $callback;
        return true;
    }
    public function callRegisteredShutdown() {
        foreach ($this->callbacks as $arguments) {
            $callback = array_shift($arguments);
            call_user_func_array($callback, $arguments);
        }
    }
    // test methods:
    public function dynamicTest() {
        echo '_REQUEST array is '.count($_REQUEST).' elements long.<br />';
    }
    public static function staticTest() {
        echo '_SERVER array is '.count($_SERVER).' elements long.<br />';
    }
}
?>

A simple application:

<?php
// a generic function
function say($a = 'a generic greeting', $b = '') {
    echo "Saying {$a} {$b}<br />";
}

$scheduler = new shutdownScheduler();

// schedule a global scope function:
$scheduler->registerShutdownEvent('say', 'hello!');

// try to schedule a dyamic method:
$scheduler->registerShutdownEvent(array($scheduler, 'dynamicTest'));
// try with a static call:
$scheduler->registerShutdownEvent('scheduler::staticTest');

?>

It is easy to guess how to extend this example in a more complex context in which user defined functions and methods should be handled according to the priority depending on specific variables.

Hope it may help somebody.
Happy coding!
clover at fromru dot com 01-Jun-2010 02:17
If you register function that needs to be running last (for example, close database connection) - just register another shutdown function from shutdown function:
<?php
function test1(){
  register_shutdown_function('test_last');
}

function test2(){/*...*/}
function test3(){/*...*/}
function test_last(){/*...*/}

register_shutdown_function('test1');
register_shutdown_function('test2');
register_shutdown_function('test3');
?>

the script will call functions in correct order: test1, test2, test3, test_last
sander @ unity-x 12-May-2010 03:42
simple method to disconnect the client and continue processing:

<?php
function endOutput($endMessage){
    ignore_user_abort(true);
    set_time_limit(0);
    header("Connection: close");
    header("Content-Length: ".strlen($endMessage));
    echo $endMessage;
    echo str_repeat("\r\n", 10); // just to be sure
    flush();
}

// Must be called before any output
endOutput("thank you for visiting, have a nice day');

sleep(100);
mail("you@yourmail.com", "ping", "i'm here");
?>
jawsper at aximax dot nl 20-Apr-2010 05:21
Something found out during testing:

the ini auto_append_file will be included BEFORE the registered function(s) will be called.
ravenswd at gmail dot com 21-Dec-2009 01:43
You may get the idea to call debug_backtrace or debug_print_backtrace from inside a shutdown function, to trace where a fatal error occurred. Unfortunately, these functions will not work inside a shutdown function.
Ant P. 02-Oct-2009 12:13
As of PHP 5.3.0, the last note about unpredictable working directory also applies to FastCGI, when previously it didn't.
Anonymous 17-Sep-2009 05:29
Note that if the handler function is private static it will never be called! It must be public!
Filip Dalge 16-Aug-2009 08:35
The following function register_close_function should reproduce the former php behavior of closing the connection before executing the shutdown handler, based on the code posted by sts at mail dot xubion dot hu. It does not work on any machine.

<?php
function register_close_function($func) {
  register_close_function::$func = $func;
  register_shutdown_function(array("register_close_function", "close"));
  ob_start();
}
class register_close_function {
  // just a container
  static $func;
  function close() {
    header("Connection: close");
    $size = ob_get_length();
    header("Content-Length: $size");
    ob_end_flush();
    flush();
    call_user_func(register_close_function::$func);
  }
}
?>
pgl at yoyo dot org 02-Aug-2009 02:25
You definitely need to be careful about using relative paths in after the shutdown function has been called, but the current working directory doesn't (necessarily) get changed to the web server's ServerRoot - I've tested on two different servers and they both have their CWD changed to '/' (which isn't the ServerRoot).

This demonstrates the behaviour:

<?php
function echocwd() { echo 'cwd: ', getcwd(), "\n"; }

register_shutdown_function('echocwd');
echocwd() and exit;
?>

Outputs:

cwd: /path/to/my/site/docroot/test
cwd: /

NB: CLI scripts are unaffected, and keep their CWD as the directory the script was called from.
cFreed at orange dot fr 14-Mar-2009 09:36
May be obvious for most people, but I spent time to clearly understand something which is only INDIRECTLY mentioned by the manual, so I hope this useful for someones.

Pay attention to the function prototype: the $function argument is a callback one (follow the link for more information).
This means that you must write this argument differently depending on the $function context:
. function-name, as a string, when it is a built-in or user-defined function
. array(class-name, method-name), when it is an object method
SonOfTron 05-Oct-2008 06:24
You can achieve similar results by using auto_append_file in the php.ini or .htaccess file:
(php.ini)
auto_append_file = /my-auto-append-file.php
(.htaccess)
php_value auto_append_file /my-auto-append-file.php
RLK 14-Sep-2008 02:26
Contrary to the the note that "headers are always sent" and some of the comments below - You CAN use header() inside of a shutdown function as you would anywhere else; when headers_sent() is false. You can do custom fatal handling this way:

<?php
ini_set('display_errors',0);
register_shutdown_function('shutdown');

$obj = new stdClass();
$obj->method();

function shutdown()
{
  if(!is_null($e = error_get_last()))
  {
    header('content-type: text/plain');
    print "this is not html:\n\n". print_r($e,true);
  }
}
?>
Fuzika 13-Aug-2007 05:27
Sinured's example of how to use a static method did not work for me.
But this did:

<?php
register_shutdown_function(array('theClass','theStaticMethod'));
?>

Hope this helps someone.

[EDIT by danbrown AT php DOT net: This example did not work for the author of this note because it is written for PHP 5.  The author was using PHP 4.]
Sinured 10-Aug-2007 06:26
You can use a static method of a class as a shutdown function without passing an instance. I think that doesn't make too much sense, however it's possible.

<?php
register_shutdown_function('someClass::someMethod');
?>

If this method is *NOT* static, then PHP will complain about an invalid callback instead of just emitting an E_STRICT error.
buraks78 at gmail dot com 01-Jul-2007 05:51
Read the post regarding the change of working directory to ServerRoot carefully. This means that require_once "path/to/script" (or similar constructs) with relative paths will not work in shutdown functions.
Ldkronos 25-Jan-2007 09:55
It's already been discussed on the zlib page ( http://www.php.net/zlib ), but hasn't been mention here...

When zlib compression is enabled, register_shutdown_function doesn't work properly. Anything output from your shutdown function will not be readable by the browser. Firefox just ignores it. IE6 will show you a blank page.

The workaround that worked for me is to add the following to the top of the script.
ini_set('zlib.output_compression', 0);
dweingart at pobox dot com 13-Mar-2006 08:53
I have discovered a change in behavior from PHP 5.0.4 to PHP 5.1.2 when using a shutdown function in conjunction with an output buffering callback.

In PHP 5.0.4 (and earlier versions I believe) the shutdown function is called after the output buffering callback.

In PHP 5.1.2 (not sure when the change occurred) the shutdown function is called before the output buffering callback.

Test code:
<?php
function ob_callback($buf) {
    $buf .= '<li>' . __FUNCTION__ .'</li>';
    return $buf;
}

function shutdown_func() {
    echo '<li>' . __FUNCTION__ .'</li>';
}

ob_start('ob_callback');
register_shutdown_function('shutdown_func');
echo '<ol>';
?>

PHP 5.0.4:

1. ob_callback
2. shutdown_func

PHP 5.1.2:

1. shutdown_func
2. ob_callback
me at thomaskeller dot biz 11-Mar-2006 02:27
Well, it might be obvious, but one should remember that one cannot send any HTTP header in the shutdown callback.

Something like

<?php

function redirect()
{
     header("Location: myuri.php");
}

register_shutdown_function("redirect");

// do something useful here

?>

doesn't work and PHP sends out the popular "headers already sent" warning.

I tried to set a redirection target somewhere in the script, but wanted to make sure that it was only set/executed at the very end of the script, since my custom redirect function also cleaned any output buffers at that point. Well, no luck here =)
kenneth dot kalmer at gmail dot com 27-Jan-2006 09:26
I performed two tests on the register_shutdown_function() to see under what conditions it was called, and if a can call a static method from a class. Here are the results:

<?php
/**
 * Tests the shutdown function being able to call a static methods
 */
class Shutdown
{
    public static function Method ($mixed = 0)
    {
        // we need absolute
        $ap = dirname (__FILE__);
        $mixed = time () . " - $mixed\n";
        file_put_contents ("$ap/shutdown.log", $mixed, FILE_APPEND);
    }
}
// 3. Throw an exception
register_shutdown_function (array ('Shutdown', 'Method'), 'throw');
throw new Exception ('bla bla');

// 2. Use the exit command
//register_shutdown_function (array ('Shutdown', 'Method'), 'exit');
//exit ('exiting here...')

// 1. Exit normally
//register_shutdown_function (array ('Shutdown', 'Method'));
?>

To test simply leave one of the three test lines uncommented and execute. Executing bottom-up yielded:

1138382480 - 0
1138382503 - exit
1138382564 - throw

HTH
sezer yalcin 26-Dec-2005 09:11
re:codeslinger at compsalot dot com

fork() is actually creating 2 processes from one. So there is no surprise register_shutdown_function will be executed per each process.

I think you have reported this as a bug and now in php 5.1.0 when you exit from child process, it does not execute it. Well, what are you going to do if you have something to register for forked process?

I hope php will be more stable near soon!

codeslinger at compsalot dot com
03-Feb-2005 09:22
Here is a nice little surprise to keep in mind...

If you register a shutdown function for your main program.  And then you fork() a child.

Guess What?
When the child exits it will run the code that was intended for the main program.  This can be a really bad thing  ;-)

Happily there is a simple work-around.  All you need to do is to create a global variable such as:

$IamaChild = [TRUE | FALSE];

and have your shutdown function check the value...
http://livejournal.com/~sinde1/ 02-Dec-2005 04:49
If you want to do something with files in function, that registered in register_shutdown_function(), use ABSOLUTE paths to files instead of relative. Because when script processing is complete current working directory chages to ServerRoot (see httpd.conf)
Niels Ganser <php dot comment at depoll dot de> 22-Sep-2005 07:58
Just a quick note: from 5.0.5 on objects will be unloaded _before_ your shutdown function is called which means you can't use previously initiated objects (such as mysqli).

See bug 33772 for more information.
codeslinger at compsalot dot com 03-Feb-2005 09:22
Here is a nice little surprise to keep in mind...

If you register a shutdown function for your main program.  And then you fork() a child.

Guess What?
When the child exits it will run the code that was intended for the main program.  This can be a really bad thing  ;-)

Happily there is a simple work-around.  All you need to do is to create a global variable such as:

$IamaChild = [TRUE | FALSE];

and have your shutdown function check the value...
astrolox at lawyersonline dot co dot uk 18-Mar-2004 11:57
When using the register_shutdown_function command in php 4. The registered functions are called in the order that you register them.

This is important to note if you are doing database work using classes that register shutdown functions for themselves.

You must register the shutdown_functions in the order that you want things to shutdown. ( ie the database needs to shutdown last )

Example of what will not work but what you might expect to work :

<?php
class database {

        function database() {
                echo "connect to sql server -- (database :: constructor)<br>\n";
                register_shutdown_function( array( &$this, "phpshutdown" ) );
                $this->connected = 1;
        }
       
        function do_sql( $sql ) {
                if ( $this->connected == 1 ) {
                        echo "performing sql -- (database :: do_sql)<br>\n";
                } else {
                        echo " ERROR -- CAN NOT PERFORM SQL -- NOT CONNECTED TO SERVER -- (database :: do_sql)<br>\n";
                }
        }
       
        function phpshutdown() {
                echo "close connection to sql server -- <b>(database :: shutdown)</b><br>\n";
                $this->connected = 0;
        }      
}

class table {
       
        function table( &$database, $name ) {
                $this->database =& $database;
                $this->name = $name;
                echo "read table data using database class -- name=$this->name -- (table :: constructor)<br>\n";
                register_shutdown_function( array( &$this, "phpshutdown" ) );
                $this->database->do_sql( "read table data" );
        }
       
        function phpshutdown() {
                echo "save changes to database -- name=$this->name -- <b>(table :: shutdown)</b><br>\n";
                $this->database->do_sql( "save table data" );
        }
}

$db =& new database();

$shoppingcard =& new table( &$db, "cart " );
?>

Output of the above example is :-

connect to sql server -- (database :: constructor)
read table data using database class -- name=cart -- (table :: constructor)
performing sql -- (database :: do_sql)
close connection to sql server -- (database :: shutdown)
save changes to database -- name=cart -- (table :: shutdown)
ERROR -- CAN NOT PERFORM SQL -- NOT CONNECTED TO SERVER -- (database :: do_sql)
Jim Smith 15-Mar-2004 04:17
I was trying to figure out how to pass parameters to the register_shutdown_function() since you cannot register a function with parameters and passing through globals is not appropriate. E.g. what I was trying to do was  <? register_shutdown_function("anotherfunction('parameter')") ?>
Turns out, the trick is to use create_function() to create a "function" that calls the desired function with static parameters.

<?php
$funtext="mail('u@ho.com','mail test','sent after shutdown');";
register_shutdown_function(create_function('',$funtext));
?>

Here's another example showing in-line logging and a post-execution version:

Before: in-process logging

<?php
function logit($message) {
   $oF=fopen('TEST.log', 'a');
   fwrite($oF,"$message\n");
   fclose($oF);
   sleep(5);  // so you can see the delay
}
print "loging";
logit("traditional execution");
print "logged";
exit;
?>
After:

<?php
function logit($message) {
   $forlater=create_function('',"loglater('$message');");
   register_shutdown_function($forlater);
}
function loglater($message) {
   $oF=fopen('TEST.log', 'a');
   fwrite($oF,"$message\n");
   fclose($oF);
   sleep(5);  // so you can see the delay
}
print "loging";
logit("delayed execution");
print "logged";
exit;
?>

In the 'before' example, the file is written (and the delay occurs) before the "logged" appears. In the 'after' example, the file is written after execution terminates.

Maybe it would be nice to add a parameter to the register_shutdown_function that does this automatically?
sts at mail dot xubion dot hu 15-Mar-2004 02:56
If you need the old (<4.1) behavior of register_shutdown_function you can achieve the same with "Connection: close" and "Content-Length: xxxx" headers if you know the exact size of the sent data (which can be easily caught with output buffering).
An example:
<?php
header("Connection: close");
ob_start();
phpinfo();
$size=ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();
sleep(13);
error_log("do something in the background");
?>

The same will work with registered functions.
According to http spec, browsers should close the connection when they got the amount of data specified in Content-Length header. At least it works fine for me in IE6 and Opera7.
James Wyse (James [at] tastyspoon.com) 12-Feb-2004 08:49
Just a note to say that if your function uses paths relative to the script you are running (ie. for reading files, "../dir/" etc) then your function may not work correctly when registered as a shutdown function. I'm not sure where the 'working dir' IS when running a shutdown function but I find it best to use absolute paths ("/home/www/dir/").
phpmanual at NO_SPHAMnetebb dot com 15-Nov-2003 08:31
Given this code:

<?php
class CallbackClass {
    function CallbackFunction() {
        // refers to $this
    }

    function StaticFunction() {
        // doesn't refer to $this
    }
}

function NonClassFunction() {
}
?>

there appear to be 3 ways to set a callback function in PHP (using register_shutdown_function() as an example):

1: register_shutdown_function('NonClassFunction');

2: register_shutdown_function(array('CallbackClass', 'StaticFunction'));

3: $o =& new CallbackClass();
   register_shutdown_function(array($o, 'CallbackFunction'));

The following may also prove useful:

<?php
class CallbackClass {
    function CallbackClass() {
        register_shutdown_function(array(&$this, 'CallbackFunction')); // the & is important
    }
   
    function CallbackFunction() {
        // refers to $this
    }
}
?>
jules at sitepointAASASZZ dot com 01-Jul-2003 12:41
If your script exceeds the maximum execution time, and terminates thusly:

Fatal error: Maximum execution time of 20 seconds exceeded in - on line 12

The registered shutdown functions will still be executed.

I figured it was important that this be made clear!
php at spandex dot deleteme dot nildram dot co dot uk 28-Apr-2003 01:43
I've had immense trouble getting any of the examples of emulated destructors to work.  They always seemed to have a copy of the object just after initialisation.  Many people mention that the register_shutdown_function will take a copy of the object rather than a reference... and this can be cured with an ampersand.  If you look in the PEAR docs for the way they emulate destructors you'll find that you also need one before the "new" statement when you create an instance of your object.  There's an editors note above that mentions this too... but I thought I'd collect it all here in one example that really works.  Honest... I'm using it (PHP 4.3.1):

<?php
class Object {
    var $somevar = "foo";

    function Object() {
        $somevar = "bar";
        register_shutdown_function(array(&$this, 'MyDestructor'));
    }

    function MyDestructor() {
        # Do useful destructor stuff here...
    }
}

# Now create the object as follows and then 'MyDestructor'
# will be called on shutdown and will be able to operate on
# the object as it ended up... not as it started!
$my_object =& new Object;
?>
kwazy at php dot net 29-Jan-2003 07:53
One more note to add about register_shutdown_function and objects.

It is possible to self-register the object from the constructor, but even using the syntax:
register_shutdown_function(array(&$this,'shutdown'))

will only result in the function being called with the object in the "just initialized" state, any changes made to the object after construction will not be there when the script actually exits.

But if you use:

<?php
$obj = new object();
register_shutdown_function(array(&$obj,'shutdown'));
?>

the object method 'shutdown' will be called with the current state of the object intact.

[Editor's note: The explanation for this behavior is really simple.
"$obj = new object()" creates a copy of the object which you can refer with $this in the object's constructor.
To solve this "problem" you should use "$obj = &new object()" which assign the reference to the current object.]
23-Oct-2002 09:35
When using CLI ( and perhaps command line without CLI - I didn't test it) the shutdown function doesn't get called if the process gets a SIGINT or SIGTERM. only the natural exit of PHP calls the shutdown function.
To overcome the problem compile the command line interpreter with --enable-pcntl and add this code:

<?php
function sigint()
{
    exit;
}
pcntl_signal(SIGINT, 'sigint');
pcntl_signal(SIGTERM, 'sigint');
?>

This way when the process recieves one of those signals, it quits normaly, and the shutdown function gets called.
Note: using the pcntl function in web server envoirment is considered problematic, so if you are writing a script that runs both from the command line and from the server, you should put some conditional code around that block that identifies wheater this is a command line envoirment or not.
adam at saki dot com dot au 20-Aug-2002 03:38
When using objects the syntax register_shutdown_function(array($object, 'function')) will take a copy of the object at the time of the call.  This means you cannot do this in the constructor and have it correctly destruct objects.  The alternative is to use register_shutdown_function(array(&$object, 'function')) where the ampersand passes the reference and not the copy.  This appears to work fine.
priebe at mi-corporation dot com 14-Mar-2002 08:25
Note that register_shutdown_function() does not work under Apache on Windows platforms.  Your shutdown function will be called, but the connection will not close until the processing is complete.  Zend tells me that this is due to a difference between Apache for *nix and Apache for Windows.

I'm seeing similar behavior under IIS (using php4isapi).
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