I have simple filtering form using WooCommerce plugin HUSKY Product Filter (previously WOOF) where customer choose product category, then choose product tag and then can write product number in Search by text field. I need to make this text field required/mandatory so if customer don't put nothing in this field submit button won't filter results. I used that code in my functions.php file for child theme, but it doesn't work, probably I take wrong field name form plugin. add_filter( 'woof_fs_by_text', 'require_search_by_text_woof'); function require_search_by_text_woof( $fields ) { $fields['woof_txt_search66e01ba5d1c01']['required'] = true; return $fields; } Page with the formular is: https://gres.info.pl/testowaa/ If anybody could help me fix the code or use another method to make this field mandatory, I would really appriciate it.