Fatal error: Uncaught Error: Call to undefined function add_filter() in C:\xampp\htdocs\wo\woocommerce\includes\class-wc-brands-coupons.php:23 Stack trace: #0 C:\xampp\htdocs\wo\woocommerce\includes\class-wc-brands-coupons.php(191): WC_Brands_Coupons->__construct() #1 {main} thrown in C:\xampp\htdocs\wo\woocommerce\includes\class-wc-brands-coupons.php on line 23