Sakrij polje za unos kupona na stranici naplate ako je već unesen na stranici košarice

/* Hide coupon form on checkout if coupon is already applied from cart */
add_filter( 'woocommerce_coupons_enabled', 'woocommerce_coupons_enabled_on_checkout' );

function woocommerce_coupons_enabled_on_checkout( $coupons_enabled ) {
    global $woocommerce;
    if ( ! empty( $woocommerce->cart->applied_coupons ) ) {
        return false;
    }
    return $coupons_enabled;
}