send_fcm_notification_with_data_to_a_topic.php

<?php
/**
 * Gist by:
 *   Md. Mahmudul Hasan Shohag
 *   imaginativeshohag@gmail.com
 *
 * Help Doc:
 * - https://firebase.google.com/docs/cloud-messaging/http-server-ref
 *
 * How to get FCM Server Kay:
 * - https://developer.clevertap.com/docs/find-your-fcm-sender-id-fcm-server-api-key
 */

/**
 * Use example:
 *
 * $data = array(
 *     'key1' => 'value1',
 *     'key2' => 'value2'
 * );
 *
 * send_notification("topic_name", "title", "message", $data);
 */


/**
 * Firebase Cloud Messaging server key.
 */
const FCM_SERVER_KEY = "";

/**
 * @param $topic string Single topic name
 * @param $title string Notification title
 * @param $message string Notification message
 * @param null|array $data
 */
function send_fcm_notification_to_a_topic($topic, $title, $message, $data = null)
{
    $fcmUrl = 'https://fcm.googleapis.com/fcm/send';


    # Notification payload
    $notification = array
    (
        'title' => $title,
        'body' => $message,
        'sound' => 'default'
    );


    if ($data == null) {
        $fields = array
        (
            'to' => "/topics/$topic",
            'notification' => $notification
        );
    } else {
        $fields = array
        (
            'to' => "/topics/$topic",
            'notification' => $notification,
            'data' => $data
        );
    }


    $headers = array
    (
        'Authorization: key=' . FCM_SERVER_KEY,
        'Content-Type: application/json'
    );


    # Send Request To Firebase Server
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $fcmUrl);
    curl_setopt($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);


    var_dump($result);
}