I received a bug report, or rather it’s outdated:
Deprecated: Creation of dynamic property MyWebSocketUser::$requestedResource is deprecated
the code looked like this:

if (isset($headers["get"])) {
  $user->requestedResource = $headers["get"];
} 

With this everything is clear and fair, because the class is empty and inherits classes that do not have this property.
But an attempt to declare such a property led to nothing. In order to exclude cache or incorrect code source, I wrapped it in a method:

if (isset($headers["get"])) {
  $user->setGet($headers["get"]);
} 

<?php
require_once(__DIR__ . '/../websockets/users.php');

class MyWebSocketUser extends WebSocketUser
{
  public $requestedResource = null;

  public function setGet($get)
  {
          $this->requestedResource = $get;
  }
}

Ubuntu, php 8.2.20, if it makes any difference