fcm.html

<!-- Firebase App is always required and must be first -->
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-app.js"></script>

<!-- Add additional services that you want to use -->
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-database.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-firestore.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-messaging.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-functions.js"></script>

<!-- Comment out (or don't include) services that you don't want to use -->
<!-- <script src="https://www.gstatic.com/firebasejs/5.7.0/firebase-storage.js"></script> -->

<script>
  // Initialize Firebase
  var config = {
    apiKey: "*****",
    authDomain: "webfcm-e49d8.firebaseapp.com",
    databaseURL: "https://webfcm-e49d8.firebaseio.com",
    projectId: "webfcm-e49d8",
    storageBucket: "webfcm-e49d8.appspot.com",
    messagingSenderId: "849978943949"
  };
  firebase.initializeApp(config);
const messaging = firebase.messaging();

messaging.usePublicVapidKey("BA2eLLCr3TsohmhQsZxROr-io6mjyv3I8uYmy3q_Dm42UaaXWyNX4JDMyO_jnvgBSPe--EprGGYp1_Zhi76qZC8");

  messaging.requestPermission().then(function() {
  console.log('Notification permission granted.');
  // TODO(developer): Retrieve an Instance ID token for use with FCM.
  // ...
}).catch(function(err) {
  console.log('Unable to get permission to notify.', err);
});

messaging.onMessage(function(payload) {
  console.log('Message received. ', payload);
  // ...
});

messaging.getToken();

</script>

testgcm.php

<?php

$request = new HttpRequest();
$request->setUrl('https://fcm.googleapis.com/fcm/send');
$request->setMethod(HTTP_METH_POST);

$request->setHeaders(array(
	'Postman-Token' => 'ee3a89ba-c548-43e9-ba13-f759468fbc53',
	'cache-control' => 'no-cache',
	'Authorization' => 'key=AAAAxeaxac0:APA91bEjOcOXWbVr-mYk0PQLxLcZnDWesnUX-q79SMVvRT5zK_zzF0HiJKKlPTAsH-I8zuaoM501xOZ9eetwj6yV6XoLOLern3Y7D9D3xBZVZiActPbpk-xVk1bmP_lTgHcE8v35BEG9',
	'Content-Type' => 'application/json',
));

$request->setBody('{
    "notification": {
        "title": "Firebase",
        "body": "Firebase is awesome",
        "click_action": "http://localhost",
        "icon": ""
    },
    "to": "cL4acO_Di5I:APA91bGr5_Z0KUOVbybGtLS_mB_RXHAecOE62RVHoXqH8ivORKRUGvNwg2t_h5eu2wpsLetuqFHoRxD6jjspb7DcQX5K85xhSyWy6JNiuX-Sa0YKnhTE8P7q3ytHW1Up0ugW8uSsEUdc"
}');

try {
	$response = $request->send();

	echo $response->getBody();
} catch (HttpException $ex) {
	echo $ex;
}