Using Firebase FCM for Push Notifications in PHP: A Complete Guide

<?php
require_once __DIR__ . '/vendor/autoload.php';

use phpFCMv1\Client;
use phpFCMv1\Notification;
use phpFCMv1\Recipient;

// Client instance should be created with path to service account key file
$client = new Client("/path/to/service_account.json");
$recipient = new Recipient();

// Either Notification or Data (or both) instance should be created
$notification = new Notification();

// Recipient could accept individual device token,
// the name of topic, and conditional statement
$recipient->setSingleREcipient('DEVICE_TOKEN');

// Setup Notificaition title and bod
$notification->setNotification('NOTIFICATION_TITLE', 'NOTIFICATION_BODY');

//if you have extra data to send to the client
if(!empty($extraData)) {
    //create a data object
    $data = new Data();

    //add extra data to the payload
    $data->setPayload(["data" => $dataArray]);

    // Build FCM request payload
    $client->build($recipient, $notification, $data);
} else {
    $client->build($recipient, $notification);
}

// You can check the result
// If successful, true will be returned
// If not, error message will be returned
$result = $client->fire();

if(!$result) {
    //do something in case of error
} else {
    //do something in case of success
}