Consik/yii2-websocket - Guzzle error while creating websocket server yii2

I’m trying to create websocket server in yii2, when I start the server from command php yii server/start it says server started on port 81 but as I try to connect it from javascript the server immediately breaks and I get this error.

PHP Fatal Error ‘yii\base\ErrorException’ with message 'During inheritance of ArrayAccess: Uncaught yii\base\ErrorException: Return type of Guzzle\Common\Collection::offsetExists($offset) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /Applications/MAMP/htdocs/namenja/vendor/guzzle/common/Guzzle/Common/Collection.php:294

Here is my console controller code for the server.

namespace console\controllers;

use consik\yii2websocket\WebSocketServer;
use yii\console\Controller;

class ServerController extends Controller
    public function actionStart()
        $server = new WebSocketServer();
        $server->port = 80; //This port must be busy by WebServer and we handle an error

        $server->on(WebSocketServer::EVENT_WEBSOCKET_OPEN_ERROR, function($e) use($server) {
            echo "Error opening port " . $server->port . "\n";
            $server->port += 1; //Try next port to open

        $server->on(WebSocketServer::EVENT_WEBSOCKET_OPEN, function($e) use($server) {
            echo "Server started at port " . $server->port;


and here is the js code

var conn = new WebSocket('ws://localhost:81');
conn.onmessage = function(e) {
    console.log('Response:' +;
conn.onopen = function(e) {
    console.log("Connection established!");

The full trace of the error can be seen here.