pcntl_signal_dispatch

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

pcntl_signal_dispatch — 调用等待信号的处理器

说明

pcntl_signal_dispatch ( ) : bool

函数pcntl_signal_dispatch()调用每个等待信号通过pcntl_signal() 安装的处理器。

返回值

成功时返回 true， 或者在失败时返回 false。

范例

Example #1 pcntl_signal_dispatch() 示例

<?php
echo "安装信号处理器...\n";
pcntl_signal(SIGHUP,  function($signo) {
     echo "信号处理器被调用\n";
});

echo "为自己生成SIGHUP信号...\n";
posix_kill(posix_getpid(), SIGHUP);

echo "分发...\n";
pcntl_signal_dispatch();

echo "完成\n";

?>

以上例程的输出类似于：

安装信号处理器...
为自己生成SIGHUP信号...
分发...
信号处理器被调用
完成

参见

User Contributed Notes

stefanis 13-May-2014 06:45
Well I misspoke before. It is not enough to process signals outside of the signal handler. They must be processed outside of the tick handler (explicit or implied). So...

Register a tick handler that calls pcntl_signal_dispatch();
In the signal handler, enqueue your signal;
In the main loop of your script, process your signals;

<?php
declare(ticks=1);
global $sig_queue;
global $use_queue;
$sig_queue = array();
$use_queue = true;   // set to false to do it the old way

function tick_handler()
{
     pcntl_signal_dispatch();
}

function sig_handler($sig)
{
     global $sig_queue;
     global $use_queue;

     if(isset($use_queue) && $use_queue)
     {
          $sig_queue[] = $sig;
     }
     else
     {
          sig_helper($sig);
     }
}

function sig_helper($sig)
{
     switch($sig)
     {
     case SIGHUP:
          $pid = pcntl_fork();
          if($pid) print("forked $pid\n");
          break;

     default:
          print("unhandled sig: $sig\n");
     }
}

pcntl_signal(SIGHUP,   "sig_handler");

while(true)
{
     if($use_queue) foreach($sig_queue as $idx=>$sig)
     {
           sig_helper($sig);
           unset($sig_queue[$idx]);
     }
     sleep(1);
}
?>
stefanis 13-May-2014 12:40
As noted by "me at subsonic dot net" calling pcntl_signal_dispatch() from within a signal handler invoked by a previous pcntl_signal_dispatch() will not trigger handlers for any new pending signals. This seems to be true even if you pcntl_exec() a new PHP processor to execute an entirely different script.

The solution seems to be to explicitly call pcntl_signal_dispatch()inside a ticks_handler() . And use sig_handler(int) as a push function to a queue. Immediately following the call to dispatch in the ticks_handler, pop your queue doing what you would have done in the signal_handler until the queue is empty.
me at subsonic dot cz 27-Jan-2014 05:33
Note that calling pcntl_signal_dispatch() from within a signal handler invoked by a previous pcntl_signal_dispatch() will not trigger handlers for any new pending signals. This means that if you write a CLI daemon which forks off child processes in response to a signal, then those child processes won't be able to respond to signals. This gave me a headache for a while as pcntl_signal_dispatch() doesn't raise any errors when this occurs. One solution is to set a flag within the signal handler and react upon it (by forking off the needed child processes) elsewhere in the parent process's main loop.
webmaster at ajeux dot com 10-Aug-2009 10:50
If you are running PHP as CLI and as a "daemon" (i.e. in a loop), this function must be called in each loop  to check if new signals are waiting dispatching.
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