Fatal error: Uncaught Error: Undefined constant "STRIPE_PUBLISHABLE_KEY" in /var/www/html/views/login.php:40 Stack trace: #0 /var/www/html/models/Router.php(65): include_once() #1 /var/www/html/models/Router.php(8): Router::route() #2 /var/www/html/index.php(22): Router::get() #3 {main} thrown in /var/www/html/views/login.php on line 40