Update README

README.md

@@ -24,11 +24,12 @@ This is an HTTP server which responds with `Hello World` to every request.
 $loop = React\EventLoop\Factory::create();
 $socket = new React\Socket\Server($loop);
 
-$http = new React\Http\Server($socket);
-$http->on('request', function ($request, $response) {
+$calllback = function (Request $request, Response $response) {
     $response->writeHead(200, array('Content-Type' => 'text/plain'));
     $response->end("Hello World!\n");
-});
+};
+
+$http = new React\Http\Server($socket, $callback);
 
 $socket->listen(1337);
 $loop->run();