limit_pcntl_fork.php

<?php
declare(ticks = 1);

$max=5;
$GLOBALS[__FILE__]['_child']=0;
//print_r($GLOBALS);exit;
// function for signal handler
function sig_handler($signo) {

    switch ($signo) {
        case SIGCHLD:
            echo "SIGCHLD received\n";
            $GLOBALS[__FILE__]['_child']--;
        }
    }

    // install signal handler for dead kids
    pcntl_signal(SIGCHLD, "sig_handler");

    for($i=0;$i<100;$i++){
        $GLOBALS[__FILE__]['_child']++;
        // we are the parent
        $child=$GLOBALS[__FILE__]['_child'];
        if ( $child > $max ){
            pcntl_wait($status);
        }
        $pid=pcntl_fork();

        if ($pid == -1) {
            die("could not fork");
        } else if ($pid) {

        } else {
            // we are the child
            $child=$GLOBALS[__FILE__]['_child'];
            echo "\t Starting new child \n";
            // presumably doing something interesting
            sleep(rand(3,5));
            exit;
        }
    }