ignore_user_abort()

(PHP 4, PHP 5, PHP 7)

设置客户端断开连接时是否中断脚本的执行

说明

ignore_user_abort([bool $value]): int

设置客户端断开连接时是否中断脚本的执行

PHP 以命令行脚本执行时，当脚本终端结束，脚本不会被立即中止，除非设置$value为TRUE，否则脚本输出任意字符时会被中止。

参数

$value: 如果设置了该值，函数会把ignore_user_abortini 的值设置为$value。如果未设置该值，函数不会改变设置，仅会返回之前的设置。

返回值

以整型返回之前的设置

范例

Example #1ignore_user_abort()例子

<?php
// Ignore user aborts and allow the script
// to run forever
ignore_user_abort(true);
set_time_limit(0);
echo 'Testing connection handling in PHP';
// Run a pointless loop that sometime 
// hopefully will make us click away from 
// page or click the "Stop" button.
while(1)
{
    // Did the connection fail?
    if(connection_status() != CONNECTION_NORMAL)
    {
        break;
    }
    // Sleep for 10 seconds
    sleep(10);
}
// If this is reached, then the 'break' 
// was triggered from inside the while loop
// So here we can log, or perform any other tasks
// we need without actually being dependent on the 
// browser.
?>

注释

在PHP尝试发送信息到客户端之前，不会检测到用户是否已中断连接。仅使用 echo 语句不能确保信息已发送，参见flush()函数。

参见

connection_aborted() 检查客户端是否已经断开
connection_status() 返回连接的状态位
Connection Handling关于PHP连接处理的完整描述。

Comment from Anonymous is not 100% valid. Time from sleep function is not counted to execution time because sleep delays program execution (see http://www.php.net/manual/en/function.sleep.php and comments). We tested it and it's true. Try this:
<?php
set_time_limit(2);
sleep(4);
echo 'hi!';
sleep(4);
echo 'bye bye!';
?>
It means, that if the loop most of the time will be at sleep (and in this case it probably be), then this script may be active for months or years even if you set time limit to one day.

If you want to simulate a crontask you must call this script once and it will keep running forever (during server uptime) in the background while "doing something" every specified seconds (= $interval):
<?php
ignore_user_abort(1); // run script in background
set_time_limit(0); // run script forever
$interval=60*15; // do every 15 minutes...
do{
  // add the script that has to be ran every 15 minutes here
  // ...
  sleep($interval); // wait 15 minutes
}while(true);
?>

It seems that this function does not work for IIS servers.
A detailed description can be found on the PHP Bug Tracking System:
https://bugs.php.net/bug.php?id=60586#1378935714

use the spiritual-coder's code below with exreme caution and do not use it unless you are an advanced user.
first of all, such a code with no bypass point can cause infinite loops and ghost threads in server. there must be a trick to break out the loop. 
i.e. you can use if (file_exists(dirname(__FILE__)."stop.txt")) break; in the loop so if you create "stop.txt", she script will stop execution.
also if you use set_time_limit(86400); instead of set_time_limit(0); your script will stop after one day.

If running a long process and the browser often close the connection, then use this function.

The script should output something to the browser in order to abort. If there is no output the script keeps on running.

Theres no point in sending anything to the browser if the user does abort. Since the user aborted, the browser wont listen even if PHP did send information to the browser.
If you want to see if the user did abort, then use error_log() or some other form of logging to find out what happened, but dont rely on the output to the browser as the only method of checking ones data.