Sending gcm to multiple users at a time from mysql database - php

Question

I'm developing an app and I'm on the final face where registered devices in the database are to receive push notifications at a time.
Currently, with the script I have, it can only send to one device. I have a table in my database called devices and the field that saves the device ID is called device_id. Please any help on how to send to multiple users?
<?php
$message = $_POST['title'];
$id = $_POST['id'];
// Replace with the real server API key from Google APIs
$apiKey = "AIzaSyDn9RPYmnlbs9*****WHKksz73klOqxM";
// Replace with the real client registration IDs
$registrationIDs = array("APA91bHhTiGeAKgphENoGH6********Blw9PspLCPAiprTSDN6mRuW3k253PZyppxgJaqPftTzYZOiWPt5C4XFVmkuqjbXp7MV3mAmpDAYM-11LdIdU0");
// Message to be sent
// Set POST variables
$url = 'https://android.googleapis.com/gcm/send';
$fields = array(
'registration_ids' => $registrationIDs,
'data' => array( "message" => $message,"title" => "Today's Devotion","id" => $id),
);
$headers = array(
'Authorization: key=' . $apiKey,
'Content-Type: application/json'
);
// Open connection
$ch = curl_init();
// Set the URL, number of POST vars, POST data
curl_setopt( $ch, CURLOPT_URL, $url);
curl_setopt( $ch, CURLOPT_POST, true);
curl_setopt( $ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true);
//curl_setopt( $ch, CURLOPT_POSTFIELDS, json_encode( $fields));
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
//curl_setopt($ch, CURLOPT_POST, true);
//curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode( $fields));
// Execute post
$result = curl_exec($ch);
// Close connection
curl_close($ch);
//echo $result;
//print_r($result);
//var_dump($result);
?>

Answer 1

Fetch all the device ids from your database as below:
$registrationIDs = array();
$query = "select device_id from devices";
while($row = $db->database_fetch_assoc($query))
{
$registrationIDs[] = $row;
}
Now pass this array to the $field array.

Answer 2

create your query to get device ids in $registrationIDs and send all to server.
// Replace with the real client registration IDs
$registrationIDs = array("APA91bHhTiGeAKgphENoGH6********Blw9PspLCPAiprTSDN6mRuW3k253PZyppxgJaqPftTzYZOiWPt5C4XFVmkuqjbXp7MV3mAmpDAYM-11LdIdU0");