Not Getting the "conferenceId" back from the API

I am using PHP Graph.

Following the guidelines at the example 2 of: https://learn.microsoft.com/en-us/graph/api/calendar-post-events?view=graph-rest-1.0&tabs=http.

Query:

array:8 [
  "Subject" => "subject"
  "Body" => array:2 [
    "ContentType" => "text"
    "Content" => "a body"
  ]
  "Start" => array:2 [
    "DateTime" => "2022-10-06T13:25:59"
    "TimeZone" => "Europe/Berlin"
  ]
  "End" => array:2 [
    "DateTime" => "2022-10-06T13:55:59"
    "TimeZone" => "Europe/Berlin"
  ]
  "organizer" => array:1 [
    "emailAddress" => array:2 [
      "name" => "a name"
      "address" => "valid@email.com"
    ]
  ]
  "isOnlineMeeting" => true
  "onlineMeetingProvider" => "teamsForBusiness"
  "attendees" => array:1 [
    0 => array:1 [
      "emailAddress" => array:2 [
        "name" => "a name"
        "address" => "valid@email.com"
      ]
    ]
  ]
]

It works, but I do not receive the conferenceId.
"onlineMeeting": {
"joinUrl": "https...",
}

No repository file, test, or entry point is named. Start by reproducing the request from the issue against the linked Microsoft Graph calendar-events documentation, then trace how the PHP SDK exposes the returned onlineMeeting data; done means the expected conferenceId behavior is established and the issue has a concrete, verifiable outcome.