Getting Started with Aerys

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Aerys is a new kind of server which has just become open source after years of work. It’s an application server completely written in PHP and based on the Amp Concurrency Framework. If you’re not familiar with Amp yet, you may want to read my previous blog post “Getting Started with Amp” first.


Aerys can be installed using Composer and requires PHP 7. Since it’s an application server, it makes sense to have it installed as local dependency instead of a global binary.

    "require": {
        "amphp/aerys": "dev-master"
    "minimum-stability": "dev"

composer install adds the executable server file vendor/bin/aerys. You can now run it with the sample configuration by simply executing vendor/bin/aerys -c vendor/amphp/aerys/demo.php. This will boot a server listening on localhost:1337. When visiting that address, you should see a “Hello, world.”


Aerys is configured using a simple PHP file, no XML, no YAML! This file contains essentially two parts, the global server configuration and a list of hosts. You can start Aerys with a specific configuration using vendor/bin/aerys -c config.php. Add -d to start it in debug mode.

Global Server Options

Global server options are configured using a constant associative array called AERYS_OPTIONS. This ensures that all server configuration is at one place and not split across multiple files. Here’s a list of the most important options.

Option Description
user If Aerys is started as root on Linux and this value is not null, it switches to that user after booting.
maxConnections Maximum number of concurrent connections.
maxKeepAliveRequests Maximum number of requests a client can issue using a single connection.
maxBodySize Maximum size of a request body. You may have to increase it when dealing with larger uploads.

You can find a complete list on GitHub, just use the property names as configuration array keys.

	"user" => "www-data",


Aerys supports multiple virtual hosts in a single instance. To add a new host, just instantiate a new instance of Aerys\Host. By default a host is exposed on port 80 and named localhost.

(new Aerys\Host)
	->expose("*", 80);

Full Configuration Example


	"user" => "www-data",

$router = Aerys\router()->get("/", function(Aerys\Request $req, Aerys\Response $resp) {
	$resp->end("<h1>Hello World!</h1>");

$docroot = Aerys\root(__DIR__ . "/public");

(new Aerys\Host)


Responders are callables invoked to dispatch requests. Every host can have as many responders as needed. Responders must have the following signature:

function(Aerys\Request $req, Aerys\Response $resp) { /* ... */ }

Responders are executed in the order they’re added to the Host object until one responder starts outputting a response body. All following responders won’t be called.

A very simple example is a responder that responds always with the same content.

(new Aerys\Host)
	->use(function(Aerys\Request $req, Aerys\Response $resp) {
		$resp->end("<h1>It Works!</h1>");


A more complex responder is the built-in router which is based on NikiC’s FastRoute.

$callable = function(Aerys\Request $req, Aerys\Response $resp, array $args) {
	$resp->end("<h1>ID: " . htmlspecialchars($args["id"]) . "</h1>");

$router = Aerys\router();
$router->route("GET", "/users/{id}", $callable);


As it’s just another responder, you can always build your own router or use any other router implementation.

Static Files

Aerys is not just an application server, but can also serve static files. The document root implementation is just another responder. Usually you want to add it as last responder, because filesystem access is slow and you want to hit your disk only if no other responder matched.

As PHP supports only blocking filesystem access by default, you should make sure to have either pecl/eio or php-uv installed in production, see amphp/file.

$docroot = Aerys\root(__DIR__ . "/public");

Advanced features

There’s still more, e.g. “Getting Started with Aerys WebSockets” or Middlewares which will be covered in a future blog post.