Fatal error: Uncaught Error: Undefined constant "self" in /var/www/html/includes/classes/Notification.class.php:20 Stack trace: #0 /var/www/html/includes/frontend-pages/subscribe.page.php(2): Notification::init() #1 /var/www/html/user_nfa/index.php(21): require_once('...') #2 {main} thrown in /var/www/html/includes/classes/Notification.class.php on line 20