Fatal error: Uncaught Error: Call to undefined function add_filter() in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-reminders/includes/admin/class-post_meta.php:9 Stack trace: #0 /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-reminders/includes/admin/class-post_meta.php(185): evorm_meta_boxes->__construct() #1 {main} thrown in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-reminders/includes/admin/class-post_meta.php on line 9