Fatal error: Uncaught Error: Call to undefined function add_filter() in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-rsvp/includes/class-intergration-actionuser.php:10 Stack trace: #0 /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-rsvp/includes/class-intergration-actionuser.php(459): evors_actionuser->__construct() #1 {main} thrown in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/eventon-rsvp/includes/class-intergration-actionuser.php on line 10