Send firebase push notification to multiple users not working -php - php

Question

I'm trying to send push notification to multiple devices using below PHP script.when i send notification to one device ,it's working.but not working for multiple devices.
protected function pushNotification($reg_id){
define( 'API_ACCESS_KEY', 'AAAAgUh9ZSQ:APA91bEjQ2nO3Po9_-T_kNey4q3Eizcoc3gLsD04Bjh0KYXQu_33O2gpLBvmMV_DtbE3xP2evZ1Dwki6WRqgqu8ZYhOG2CYi-6Wpxq2CLy3SQPb1nD6QkzwNN0249pt-H2mAgB8L-sjm' );
$registrationIds = array($reg_id);
$msg = array
(
'body' => 'Hey! You have a new order in queue',
'title' => 'New Order Receieved',
'icon' => 'myicon',/*Default Icon*/
'sound' => 'mySound'/*Default sound*/
);
$fields = array
(
'to' => $registrationIds,
'notification' => $msg
);
$headers = array
(
'Authorization: key=' . API_ACCESS_KEY,
'Content-Type: application/json'
);
$ch = curl_init();
curl_setopt( $ch,CURLOPT_URL, 'https://fcm.googleapis.com/fcm/send' );
curl_setopt( $ch,CURLOPT_POST, true );
curl_setopt( $ch,CURLOPT_HTTPHEADER, $headers );
curl_setopt( $ch,CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER, false );
curl_setopt( $ch,CURLOPT_POSTFIELDS, json_encode( $fields ) );
$result = curl_exec($ch );
curl_close( $ch );
error_log("Result ".$result) ;
}

Answer 1

The problem lies in your use of to in $fields. to is to be used only when you have an individual String FCM ID. If you want to send notifications to an array of FCM IDs (which is your case), you must use registration_ids in place of to. Please note that you can only pass an array of size lesser than 1000 at a time in this operation.
For more information, https://firebase.google.com/docs/cloud-messaging/http-server-ref .