Add example for behind proxy

examples/behind-proxy.php

@@ -0,0 +1,58 @@
+#!/usr/bin/env php
+<?php
+
+require dirname(__DIR__) . "/vendor/autoload.php";
+
+use Amp\ByteStream;
+use Amp\Http\HttpStatus;
+use Amp\Http\Server\DefaultErrorHandler;
+use Amp\Http\Server\Middleware\Forwarded;
+use Amp\Http\Server\Middleware\ForwardedHeaderType;
+use Amp\Http\Server\Request;
+use Amp\Http\Server\RequestHandler;
+use Amp\Http\Server\Response;
+use Amp\Http\Server\SocketHttpServer;
+use Amp\Log\ConsoleFormatter;
+use Amp\Log\StreamHandler;
+use Monolog\Logger;
+use Monolog\Processor\PsrLogMessageProcessor;
+use function Amp\trapSignal;
+
+// Example configuration for a server to be run behind a proxy such as nginx.
+
+$logHandler = new StreamHandler(ByteStream\getStdout());
+$logHandler->pushProcessor(new PsrLogMessageProcessor());
+$logHandler->setFormatter(new ConsoleFormatter());
+$logger = new Logger('server');
+$logger->pushHandler($logHandler);
+$logger->useLoggingLoopDetection(false);
+
+$server = SocketHttpServer::createForBehindProxy(
+    logger: $logger,
+    headerType: ForwardedHeaderType::XForwardedFor,
+    trustedProxies: ["172.18.0.0/24"],
+);
+
+$server->expose("0.0.0.0:8080");
+
+$server->start(new class implements RequestHandler {
+    public function handleRequest(Request $request): Response
+    {
+        /** @var Forwarded|null $forwarded */
+        $forwarded = $request->getAttribute(Forwarded::class);
+        $for = $forwarded?->getFor() ?? $request->getClient()->getRemoteAddress();
+
+        return new Response(
+            status: HttpStatus::OK,
+            headers: ["content-type" => "text/plain; charset=utf-8"],
+            body: "Hello, " . $for->toString(),
+        );
+    }
+}, new DefaultErrorHandler());
+
+// Await a termination signal to be received.
+$signal = trapSignal([\SIGHUP, \SIGINT, \SIGQUIT, \SIGTERM]);
+
+$logger->info(sprintf("Received signal %d, stopping HTTP server", $signal));
+
+$server->stop();