Precisa enviar notificação em um lote de 1000

    // Chunk of Array with 999 Records, I have not taken risk for 1000 users :D
    // Here $array is a collection of rows which you get from Table.
    $final_array = array_chunk($array, 999);

    // Loop for Every Sub Array and Send to FCM Server
    foreach($final_array as $array_of_chunk) {

        // Your code for sending notification...
        // $registrationIds = $array_of_chunk;

    }