Forking in PHP 7 done right. No zombies!!

forking.php

<?php

/**
 * Forking in PHP 7 done right. Requires PHP >= 7.1 and Process Control extension (pcntl)
 *
 * @author Sebastian Pająk
 * Good article in the subject that inspired me: https://ruslanspivak.com/lsbaws-part3
 */

// Enable asynchronous signal handling (as of PHP 7.1)
pcntl_async_signals(true);

// How many children to fork
define('MAX_CHILDREN', 10);

function console($message) {
    file_put_contents('php://stdout', $message."\n");
}

// Function that gets called in a forked process
function childProcess() {
    $pid = getmypid();
    console("    We are now in a child process. PID: $pid");
    sleep(5);
    console("    Finishing child process. PID: $pid");
}

// Register handler for signal that is sent to a parent process whenever
// one of its child processes terminates or stops.
$result = pcntl_signal(SIGCHLD, function($signo, $siginfo) {
    // Killing zombies :)
    console("Got SIGCHLD signal");
    while (0 != $pid = pcntl_wait($status, WNOHANG)) {
        if ($pid == -1) return;
    }
});

if (false === $result) {
    throw new RuntimeException('Could not register SIGCHLD signal!');
}

// Register handler for signal that is sent when the user types the INTR character
// (normally Ctrl+c).
$result = pcntl_signal(SIGINT, function($signo, $siginfo) {
    console("Got SIGINT signal");
    console("Waiting for children to finish...");
    while (0 < pcntl_wait($status, WNOHANG)) {
        usleep(20000);
    }
    console("Stopping master process");
    // Restore default handlers. Probably not needed here as we are dying anyway.
    // But it may be used in other situations.
    pcntl_signal(SIGCHLD, SIG_DFL);
    pcntl_signal(SIGINT, SIG_DFL);
    exit(0);
});

if (false === $result) {
    throw new RuntimeException('Could not register SIGINT signal!');
}

console("Starting master process");
$count = 0;

// Master loop. Creates a new child every 1 sec
while ($count < MAX_CHILDREN) {
    if (-1 === $pid = pcntl_fork()) {
        throw new RuntimeException('Could not fork!');
    }
    if (0 === $pid) { // <=== If true then we are inside a forked process
        childProcess();
        exit(0);
    }
    $count += 1;
    sleep(1);
}

console("Master process has done his job. Sleeping...");

while (true) {
    sleep(1);
}