The code before isnt working for me cause the children are correctly started but not refreshed after they died. So keep in mind to use this instead and use the signal handler to know when a child exits to know when you have to start a new one. I added a few lines to the posting from {andy at cbeyond dot net} cause his post wasnt working for me as well (PHP5.1). Same effect like the one below.
<?php
declare(ticks = 1);
$max=5;
$child=0;
// function for signal handler
function sig_handler($signo) {
global $child;
switch ($signo) {
case SIGCHLD:
echo "SIGCHLD received\n";
$child--;
}
}
// install signal handler for dead kids
pcntl_signal(SIGCHLD, "sig_handler");
while (1){
$child++;
$pid=pcntl_fork();
if ($pid == -1) {
die("could not fork");
} else if ($pid) {
// we are the parent
if ( $child >= $max ){
pcntl_wait($status);
$child++;
}
} else {
// we are the child
echo "\t Starting new child | now we de have $child child processes\n";
// presumably doing something interesting
sleep(rand(3,5));
exit;
}
}
?>
pcntl_wait
Description
int pcntl_wait ( int &status [, int options] )The wait function suspends execution of the current process until a child has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function. If a child has already exited by the time of the call (a so-called "zombie" process), the function returns immediately. Any system resources used by the child are freed. Please see your system's wait(2) man page for specific details as to how wait works on your system.
pcntl_wait() returns the process ID of the child which exited, -1 on error or zero if WNOHANG was provided as an option (on wait3-available systems) and no child was available.
If wait3 is available on your system (mostly BSD-style systems), you can provide the optional options parameter. If this parameter is not provided, wait will be used for the system call. If wait3 is not available, providing a value for options will have no effect. The value of options is the value of zero or more of the following two constants OR'ed together:
表格 1. Possible values for options if wait3 is available
| WNOHANG | Return immediately if no child has exited. |
| WUNTRACED | Return for children which are stopped, and whose status has not been reported. |
pcntl_wait() will store status information in the status parameter which can be evaluated using the following functions: pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig() and pcntl_wstopsig().
注: This function is equivalent to calling pcntl_waitpid() with a -1 pid and no options.
See also pcntl_fork(), pcntl_signal(), pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig(), pcntl_wstopsig() and pcntl_waitpid().
add a note
User Contributed Notes
thomas dot nicolai at unisg dot ch
25-Mar-2006 03:19
25-Mar-2006 03:19
federico at nextware dot it
20-Feb-2006 08:39
20-Feb-2006 08:39
This a simple multi process application where you can choose
the maximun process that can run at the same time.
This is useful when you need to limit the fork of process.
When the MAXPROCESS is reached the program wait on pcntl_wait()
<?
DEFINE(MAXPROCESS,25);
for ($i=0;$i<100;$i++){
$pid = pcntl_fork();
if ($pid == -1) {
die("could not fork");
} elseif ($pid) {
echo "I'm the Parent $i\n";
$execute++;
if ($execute>=MAXPROCESS){
pcntl_wait($status);
$execute--;
}
} else {
echo "I am the child, $i pid = $pid \n";
sleep(rand(1,3));
echo "Bye Bye from $i\n";
exit;
}
}
?>
thisisroot at gmail dot com
19-Oct-2005 10:14
19-Oct-2005 10:14
Below is a simple example of forking some children and timing the total duration (useful for stress tests).
<?php
$isParent = true;
$children = array();
$start = microtime( true);
/* Fork you!
* (Sorry, I had to)
*/
$ceiling = $CONCURRENCY - 1;
for ( $i = 0; (( $i < $ceiling) && ( $isParent)); $i++) {
$pid = pcntl_fork();
if ( $pid === 0) {
$isParent = false;
} elseif ( $pid != -1) {
$children[] = $pid;
}
}
/* Process body */
echo "Do stuff here\n";
/* Cleanup */
if ( $isParent) {
$status = null;
while ( count( $children)) {
pcntl_wait( $status);
array_pop( $children);
}
echo "Completed in " . ( microtime( true) - $start) . " seconds.\n";
}
?>