Android和FCM，一条消息中注册ID的最大数量？

Question

My answer is simple. What is the maximal number of registered id's I can send within one message in php by using FCM.

$fields = array
(
      'registration_ids'      => $registrationIds,
      'notification'          => $notif,
      'data'                  => $data
);

Other formulated: How many Id's can i push with

array_push($registrationIds,$id);

to registrationIds?

I found out that by around 500 id's the message was received by the last id, but by 1000 not. So is there a maximum or what could be the problem?

Answer 1

From offical FCM Http Protocol, it says

registration_ids : It must contain at least 1 and at most 1000 registration tokens.

So Maximum number is 1000.