[UPHPU] Forking A Script

[Ken Snyder]

Scott Hill wrote:
> On 7/23/07, *Orson Jones* <orson.uphpu at bookstore.usu.edu 
> <mailto:orson.uphpu at bookstore.usu.edu>> wrote:
>
>     Looking around php.net <http://php.net> I found this
>
>     http://us2.php.net/manual/en/function.pcntl-fork.php
>
>     You can do a standard fork() using php. Check it out.
>
>     Orson
>
>
>
> If you don't care about the child process after it is finished, you 
> must do a pcntl_signal(SIGCHLD,SIG_IGN); before the fork.  This will 
> make the parent process ignore any signal sent back by a dying child.  
> When the child process sees that it's kill signal was either processed 
> or ignored, it dies quietly.  This prevents what is known as zombie or 
> orphan processes in *nix, which is a dead child process that has been 
> shunned by its parent.  If you want to track the process of the child 
> process, leave out the pcntl_signal and use pcntl_waitpid after the 
> fork.  This is a very, very common occurance in the *nix world.  For 
> example, the apache server forks a child process for every request on 
> its socket(s).  And I don't care what anyone says (about XP or Vista), 
> Windows still sucks when it comes to forking any kind of process.
>
> My humble $.02.
I think I've got pcntl_fork() working (see below).  The tricky part is 
that pcntl_* functions can only be called in cgi mode (i.e. from the 
command line).  One thing that is puzzling is that $argv[0] equals 
'fork.php' in sleep.php. 

I haven't yet tested to see if this works on Windows.  You mention 
Windows--are you saying that this would probably fail on Windows 2003 
Server? (My target platforms are Win 2003 Server and CentOS Linux)

With this setup, it looks like I might be able to make a Fork class so 
that I can fork any file with something like Fork::spawn($filename);.  
It would require exec() access, but that is required for this particular 
environment anyway.

-- Ken



fork.php:
<?php
$path = '/home/ksnyder/www/test/sleep.php';
exec("php $path");
echo "<p>Called script $path and didn't wait for return value</p>";
?>

sleep.php:
<?php
$logfile = '/home/ksnyder/www/test/sleep.log';

if (!function_exists('pcntl_fork')) {
  die('Error: function pcntl_fork does not exist');
}
pcntl_signal(SIGCHLD, SIG_IGN);
$pid = pcntl_fork();
if ($pid == -1) {
  // Something went wrong (handle errors here)
  file_put_contents($logfile, "Error, unable to fork!");
} elseif ($pid == 0) {
  // This part is only executed in the child
  sleep(10);
  file_put_contents($logfile, date('Y-m-d H:i:s') . ' ' 
.print_r($argv,true));
} else {
  // This part is only executed in the parent
  exit(0);
}
?>