Fatal error: Uncaught Error: Call to undefined function WP_STATISTICS\add_action() in /home/yarhsjou/public_html/wp-content/plugins/wp-statistics/includes/class-wp-statistics-referred.php:27 Stack trace: #0 /home/yarhsjou/public_html/wp-content/plugins/wp-statistics/includes/class-wp-statistics-referred.php(321): WP_STATISTICS\Referred->__construct() #1 {main} thrown in /home/yarhsjou/public_html/wp-content/plugins/wp-statistics/includes/class-wp-statistics-referred.php on line 27