WebhookController.php

<?php
// fb-bot-tutorial/app/Http/Controllers/WebhookController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class WebhookController extends Controller
{
    // this will verify the Facebook Messenger with our Laravel project
    public function getWebhook(Request $request) 
    {
		if ($request->get('hub_mode') == 'subscribe' and $request->get('hub_verify_token') === env('HUB_VERIFY_TOKEN')) {

			return response($request->get('hub_challenge'));
		}

		return response('Error, verify token doesn\'t match', 400);
	}


    //whenever Facebook Messenger get message from the user, 
    //Facebook Messenger will send to our Laravel project here
	public function postWebhook(Request $request)
	{
		$content = json_decode($request->getContent() , true);

		//check if the content of the request contain messaging property, if not exist set it as null
		$postArray = isset($content['entry'][0]['messaging']) ? $content['entry'][0]['messaging'] : null;
		$response = [];
		$has_message = false;
		$is_echo = true;
	

		if (!is_null($postArray)) {
			$sender = $postArray[0]['sender']['id'];
			$has_message = isset($postArray[0]['message']['text']);

			//if the message contain is_echo, it means it doesnt contain user message
			$is_echo = isset($postArray[0]['message']['is_echo']);
		}


		if ($has_message && !$is_echo) {

			//for now, we will just reply back the same thing as user send
			$reply = $postArray[0]['message']['text'];
			$response = $this->sendToFbMessenger($sender, $reply);
		}

		return response($response, 200);
	}


	//after we process the message on above, let send message to the user
	//back in Facebook Messenger
	protected function sendToFbMessenger($sender, $message)
	{
		//message		
		$data = ['json' => 
					[
						'recipient' => ['id' => $sender],
						'message' => ['text' => $message],
					]
				];

		$client = new \GuzzleHttp\Client;
		$res = $client->request('POST', 'https://graph.facebook.com/v2.6/me/messages?access_token='.env('FB_TOKEN'),  $data);

		return $res->getBody();
	}
}