test.php

<?php
$test_data = [
    'A' => 5,
    'B' => 3,
    'C' => 10,
    'D' => 2
];

$child_process = [];

foreach ($test_data as $key => $time) {
    $fork = pcntl_fork();
    if ($fork == -1) {
        echo 'Gagal membuat child process...' . PHP_EOL;
    }

    if ($fork > 0) {
        echo sprintf("%s:\t %s  -start -sleeps %d" .  PHP_EOL, date('h:i:sa', time()), $key, $time);
        $child_process[$fork] = $key; // masukan id child process kedalam array
    } else {
        // Code yang dijalankan didalam child process
        sleep($time);
        exit(0); // << penting supaya tidak terjadi zombie child
    }
}

// Tunggu hingga semua child selesai
while(count($child_process) !== 0) {
    foreach ($child_process as $process_id => $key) {
        $waitstatus = pcntl_waitpid($process_id, $retcode, WNOHANG);

        if ($waitstatus == -1 || $waitstatus > 0) {
            // Child sudah selesai
            echo sprintf("%s:\t %s  -finish" . PHP_EOL, date('h:i:sa', time()), $child_process[$waitstatus]);
            unset($child_process[$waitstatus]);
        }
    }
}