You can add your own rule to Better Coupon Restrictions by adding a function to the bcrw_validation_checks filter. Your check runs alongside the built-in ones, and its rejections show in the shop manager hint and in rejection analytics.

How checks work

Each check is a callable that receives the coupon and the cart:

• WC_Coupon $coupon: the coupon being validated.
• WC_Cart $cart: the current cart. Checks only run when a cart exists.

If the rule passes, return nothing. If it fails, call bcrw_fail( $message, $coupon, $section, $value ). It throws an exception that WooCommerce turns into the coupon error, and the remaining checks are skipped.

Example: block a coupon for gift cards

This PHP snippet adds a check that rejects coupons with a _mysite_no_gift_cards meta value of yes when the cart contains a product from the gift-cards category.

add_filter( 'bcrw_validation_checks', function ( $checks ) {
    $checks[] = 'mysite_check_no_gift_cards';
    return $checks;
} );

add_filter( 'bcrw_validation_check_labels', function ( $labels ) {
    $labels['mysite_check_no_gift_cards'] = 'No Gift Cards';
    return $labels;
} );

function mysite_check_no_gift_cards( $coupon, $cart ) {
    if ( 'yes' !== get_post_meta( $coupon->get_id(), '_mysite_no_gift_cards', true ) ) {
        return;
    }
    foreach ( $cart->get_cart() as $item ) {
        if ( has_term( 'gift-cards', 'product_cat', $item['product_id'] ) ) {
            bcrw_fail(
                __( 'This coupon cannot be used on gift cards.', 'mysite' ),
                $coupon,
                'cart'
            );
        }
    }
}

Tips

• Use a named function, not a closure. The function name is what appears in analytics and in the admin hint. Closures are labelled “Custom check”.
• Add a label with bcrw_validation_check_labels, otherwise the name is built from the function name.
• Custom messages: the third argument of bcrw_fail() is a section key. Passing an existing section such as cart means that section’s Custom Error Message replaces your default, with {value} swapped for the fourth argument. Adding a new key with bcrw_message_sections does not add a field to the coupon screen or save one, so you would need to handle that yourself.
• Read saved values with bcrw_get_restriction( $coupon, $meta_key, $default ) so global overrides apply.
• Cache lookups within the page load with bcrw_remember( $key, $callback ), as WooCommerce validates coupons several times per request.
• Customer details: bcrw_get_customer_email( $cart ) returns the billing or account email, or an empty string when unknown. Return early when it is empty so guests can be re-checked at checkout.
• Order: checks run in array order. Prepend to run before the built-in checks.

Related

• Hooks and filters reference
• Coupon meta keys and stored data