PHP PCNTL example

<?php

$procs = 4;
$iterations = 10;
$pids = array();

$iproc = -1;

function my_launch($i, $proc) {
    echo "Process $proc ran iteration $i.\n";
}

$pid = 0;
for ($i = 0; $i < $procs; $i++) {
    $pid = pcntl_fork();
    if ($pid > 0) {
        // I am the parent process
        $pids[$pid] = $pid;

    } elseif ($pid == -1) {
        //error occurred, use available processes only
        $nproc = $i;
        break;

    } else {
        //I am the child process.
        $iproc = $i;
        break;
    }
}

$nproc = !empty($nproc) ? $nproc : $procs;

if ($nproc == 0) {
    echo "NOTICE: Process could not be forked; proceeding in serial.\n";
    for ($i = 0; $i < $iterations; $i++) {
        my_launch($i, $iproc);
    }
    exit;
}

if ($nproc != $procs) {
    echo "NOTICE: Only using $nprocs processes out of the hoped $procs.\n";
}

$iterationsPerProcess = (int) ($iterations / $nproc);

// children do the main work.
if ($pid == 0) {
    $stopAt = $iterationsPerProcess * ($iproc + 1);

    for ($i = ($iproc * $iterationsPerProcess); $i < $stopAt; $i++) {
        my_launch($i, $iproc);
    }
}

if ($pid > 0) {
    // parent process picks up the remainder of the work
    $i = $nproc * ((int) ($iterations / $nproc));
    for (; $i < $iterations; $i++) {
        my_launch($i, "Main");
    }

    //wait for children to finish
    $status = -1;
    foreach ($pids as $createdIndex => $pid) {
        pcntl_waitpid($pid, $status);
    }
}