Fatal error: Uncaught Facebook\Exceptions\FacebookSDKException: Required "app_id" key not supplied in config and could not find fallback environment variable "FACEBOOK_APP_ID" in E:\xampp\htdocs\firstview\core\library\facebook\Facebook.php:139 Stack trace: #0 E:\xampp\htdocs\firstview\core\controllers\facebook.php(36): Facebook\Facebook->__construct(Array) #1 E:\xampp\htdocs\firstview\core\app.php(162): require('E:\\xampp\\htdocs...') #2 E:\xampp\htdocs\firstview\index.php(25): require('E:\\xampp\\htdocs...') #3 {main} thrown in E:\xampp\htdocs\firstview\core\library\facebook\Facebook.php on line 139