PHP で port 80 を開いたあと root 権限を捨てる web サーバの例

$ composer require react/react:\*
$ vim index.php
$ sudo php index.php

index.php

<?php
use React\EventLoop\Factory;
use React\Socket\Server as SocketServer;
use React\Http\Server as HttpServer;
use React\Http\Request;
use React\Http\Response;

require __DIR__ . '/vendor/autoload.php';

$loop = Factory::create();
$socket = new SocketServer($loop);
$http = new HttpServer($socket);

$http->on('request', function (Request $request, Response $response) {
    $uid = posix_getuid();
    $euid = posix_geteuid();
    $name = posix_getpwuid($uid)['name'];
    $response->writeHead();
    $response->write("Hello $request->remoteAddress\n");
    $response->write("I am $name, uid is $uid($euid)\n");
    $response->end();
});

$uid = posix_getpwnam('apache')['uid'] or die(__LINE__);
$socket->listen(80, '0.0.0.0');
posix_setuid($uid) or die(__LINE__);
$loop->run();

$ curl http://localhost/
Hello 127.0.0.1
I am apache, uid is 48(48)