PHP standalone application server.

server.php

<?php

$server = stream_socket_server(
    'tcp://127.0.0.1:8080',
    $error_no,
    $error_str,
    STREAM_SERVER_LISTEN | STREAM_SERVER_BIND,
    stream_context_create([
        'socket' => [
            'backlog' => 1024
        ]
    ])
);

$worker = 4;
$pids = [];

for ($i=0; $i<$worker; $i++) {
    $pid = pcntl_fork();

    if ($pid == -1) {
        die('don\'t fork process.' . "\n");
    } elseif($pid) {
        $pids[] = $pid;
    } else {
        unset($pids);
        break;
    }

}

// master process.
if ($pids) {
    while (true) {
        foreach ($pids as $i => $pid) {
            $res = pcntl_waitpid($pid, $status, WNOHANG);

            if ($res == -1 || $res > 0) {
                unset($pids[$i]);
            }
        }

        sleep(1);
    }
// child process.
} else {
    while (true) {
        if ($con = @stream_socket_accept($server)) {
            $_ = fread($con, 8196);

            ob_start();
            include 'index.php';
            $body = ob_get_clean();

            $header = "HTTP/1.1 200 OK\n" .
                "Content-Type: text/html; charset=UTF-8\n" .
                "Content-Length: " . strlen($body) . "\n" .
                "Connection: Close\n";

            stream_socket_sendto($con, $header . "\n" . $body);
            stream_socket_shutdown($con, STREAM_SHUT_RDWR);
        }
    }
}