(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)
pcntl_waitpid — Waits on or returns the status of a forked child
Suspends execution of the current process until a child as specified by
the process_id argument 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 as requested by process_id 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 waitpid(2) man page for specific details as to
how waitpid works on your system.
process_id
The value of process_id can be one of the following:
< -1 |
wait for any child process whose process group ID is equal to
the absolute value of process_id.
|
-1 |
wait for any child process; this is the same behaviour that the wait function exhibits. |
0 |
wait for any child process whose process group ID is equal to that of the calling process. |
> 0 |
wait for the child whose process ID is equal to the value of
process_id.
|
Note:
Specifying
-1as theprocess_idis equivalent to the functionality pcntl_wait() provides (minusflags).
status
pcntl_waitpid() 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().
flags
The value of flags is the value of zero
or more of the following two global constants
OR'ed together:
WNOHANG |
return immediately if no child has exited. |
WUNTRACED |
return for children which are stopped, and whose status has not been reported. |
pcntl_waitpid() returns the process ID of the
child which exited, -1 on error or zero if WNOHANG was used and no
child was available
please note, if you using configure option --enable-sigchild(Enable PHP's own SIGCHLD handler) when complie php(under linux 2.6.18-53.1.13.el5.centos.plus and php 5.2.5 as I know), pcntl_waitpid and pcntl_wait in php script would never return the child pid, because the build in handle get it first.<?php
$childs = array();
// Fork some process.
for($i = 0; $i < 10; $i++) {
$pid = pcntl_fork();
if($pid == -1)
die('Could not fork');
if ($pid) {
echo "parent \n";
$childs[] = $pid;
} else {
// Sleep $i+1 (s). The child process can get this parameters($i).
sleep($i+1);
// The child process needed to end the loop.
exit();
}
}
while(count($childs) > 0) {
foreach($childs as $key => $pid) {
$res = pcntl_waitpid($pid, $status, WNOHANG);
// If the process has already exited
if($res == -1 || $res > 0)
unset($childs[$key]);
}
sleep(1);
}
?><?php
declare(ticks = 1);
function zp_handler($signal) {
$id = pcntl_waitpid(-1, $status, WNOHANG);
if (pcntl_wifexited($status))
{
printf("Removed Chlid id: %d \n",$id);
printf("Chlid status: %d \n",pcntl_wexitstatus($status));
}
}
//pcntl_signal_dispatch();
pcntl_signal(SIGCHLD, "zp_handler");
//pcntl_signal_dispatch();
//
$pid = pcntl_fork();
if ($pid == 0)
{
print "#1 Hi, I'm child process".PHP_EOL;
sleep(3);
return 10;
}
else
{
print "#1parent process id:".$pid.PHP_EOL;
$pid = pcntl_fork();
if ($pid == 0)
{ print "#2 Hi, I'm child process".PHP_EOL;
sleep(10);
exit(20);
}
else
{
print "#2parent process id:".$pid.PHP_EOL;
for ($i=0; $i <10 ; $i++) {
print "wait..".PHP_EOL;
sleep(10);
}
}
}
?>