InvalidRegistration on sending push to muliple devices - php

Question

I'm trying to send push notifications to multiple device using Google Firebase and I always received the error : "InvalidRegistration".
This is the tokens that I sent in the "to"
:json_encode($tokensPerEvent):
["eV9g4oTwjZs:APA91bF3YLGtDkCDekvR6eahbVAn-jIY0sVGjxMWyBEyR-
3AB9q6RBhw4fyeqE4ZkZxQs0TsYhUee9Txy_exAGxtrBPV_-
sjKlWcV3z3nDYXOcVSVwlpPyGzUJKxGMU16drMR41bLI4t"]
and this is the response :
{
"multicast_id":***,
"success":0,
"failure":1,
"canonical_ids":0,
"results":[
{
"error":"InvalidRegistration"
}
]
}
another questions: if the one of the tokens not exist anymore, this is effect on all the other tokens , or just the only old one will effected ?
This is my code:
<?php
require_once '../CommonFunctions.php';
ignore_user_abort();
ob_start();
$url = 'https://fcm.googleapis.com/fcm/send';
//GET TOKENS FROM DB
$db = new Database();
$db->query("SELECT push_token FROM User");
$db1 = new Database();
$db1->query("SELECT phone FROM invite_list where event_id = 137");
$response = $db->resultset();
$response1 = $db1->resultset();
$arr2 = array_column($response1, 'phone');
$phones = join("','",$arr2);
$db2 = new Database();
$db2->query("SELECT push_token FROM User WHERE phone IN ('$phones')");
$tokensPerEvent = array();
$tokensrr = $db2->resultset();
$tokensPerEvent = array_column($tokensrr, 'push_token');
echo json_encode($tokensPerEvent);
$fields = array('to' => json_encode($tokensPerEvent),
'notification' => array('body' => 'HI', 'title' => ':)'));
define('GOOGLE_API_KEY', '***********');
$headers = array(
'Authorization:key='.GOOGLE_API_KEY,
'Content-Type: application/json'
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
$result = curl_exec($ch);
if($result === false)
die('Curl failed ' . curl_error());
curl_close($ch);
return $result;
?>

Answer 1

If you want to send push notification to many clients by theirs registration ids, you have to use registration_ids instead of to field. You can find this in docs (second parameter).
You are also encoding tokens two times:
$fields = array('to' => json_encode($tokensPerEvent), ...
and
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
Try by skipping encoding $tokensPerEvent in array:
$fields = array('to' => $tokensPerEvent, ...