PHP Australia Conference 2015

pcntl_signal_dispatch

(PHP 5 >= 5.3.0)

pcntl_signal_dispatchCalls signal handlers for pending signals

Descrierea

bool pcntl_signal_dispatch ( void )

The pcntl_signal_dispatch() function calls the signal handlers installed by pcntl_signal() for each pending signal.

Valorile întoarse

Întoarce valoarea TRUE în cazul succesului sau FALSE în cazul eșecului.

Exemple

Example #1 pcntl_signal_dispatch() example

<?php
echo "Installing signal handler...\n";
pcntl_signal(SIGHUP,  function($signo) {
     echo 
"signal handler called\n";
});

echo 
"Generating signal SIGHUP to self...\n";
posix_kill(posix_getpid(), SIGHUP);

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

echo 
"Done\n";

?>

Exemplul de mai sus va afișa ceva similar cu:

Installing signal handler...
Generating signal SIGHUP to self...
Dispatching...
signal handler called
Done

Vedeți de asemenea

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User Contributed Notes 4 notes

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2
webmaster at ajeux dot com
5 years ago
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.
up
1
me at subsonic dot cz
8 months ago
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.
up
0
stefanis
4 months ago
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);
}
?>
up
0
stefanis
4 months ago
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.
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