Issue with VAT Field Validation in WPFunnels checkout when using FakturaXL plug

I discovered that this problem is not related to Woocommerce FakturaXL, but to the WPFunnels checkout widget (Elementor) itself.

Explaining once again:

I have created additional fields in Checkout Field Editor for WooCommerce (Pro) for my checkout purposes:

1. checkbox – “I want to receive an invoice”
2. and 2 more fields – “company name” and NIP (VAT), which appear only when “I want to receive an invoice” is checked, and hide when uchecked.

The problem is that the first time I check the box “I want to receive an invoice” and enter an invalid NIP number, the code that validates its correctness works, but when I uncheck this checkbox and check it again, the validation no longer works (really strange behavior). This problem occurs regardless of whether the Woocommerce FakturaXL plugin is enabled or not, so it has nothing in common with it.

I’ll add that after the WPFunnels checkout page loads, all I have to do is check the checkbox “I want to receive an invoice”, uncheck it and check it again and then enter the wrong NIP (VAT) and the validation no longer works.

To sum up – after checking the checkbox “I want to receive an invoice” for the first time and entering the wrong NIP, the validation works, after unchecking the checkbox and checking it again the validation no longer works.

I should add that in the standard Elementor checkout widget this problem does not occur – the snippet validates the correctness of the NIP (VAT) field always, no matter how many times I check or uncheck the checkbox “I want to receive an invoice”.

So the problem is with WPFunnels.

Hi @cssultan, sorry for the delay – I was on vacation.

I found a solution of this issue. I added this php snippet:

add_filter( 'woocommerce_checkout_get_value', 'uncheck_billing_vat_on', 10, 2 );

function uncheck_billing_vat_on( $value, $input ) {
if ( $input === 'billing_vat_on' ) {
return '';
}
return $value;
}

and changed the snippet with VAT validation:

// Zapisujemy stan checkboxa w sesji
add_action('woocommerce_checkout_process', 'save_vat_checkbox_state');
function save_vat_checkbox_state() {
    WC()->session->set('billing_vat_on', isset($_POST['billing_vat_on']) ? true : false);
}

// Modyfikujemy funkcję walidującą NIP
add_filter('woocommerce_checkout_posted_data', 'sanitize_and_validate_billing_vat_number');
function sanitize_and_validate_billing_vat_number($data) {
    $billing_vat_on = WC()->session->get('billing_vat_on');
    
    if ($billing_vat_on) {
        $billing_vat_number = isset($data['billing_vat_number']) ? $data['billing_vat_number'] : '';
        
        // Jeśli pole NIP jest puste, nie dodajemy błędu
        if (empty($billing_vat_number)) {
            return $data;
        }

        // Usuwa spacje i myślniki z numeru NIP
        $billing_vat_number = str_replace([' ', '-'], '', $billing_vat_number);

        // Sprawdza, czy numer NIP ma 10 cyfr
        if (!preg_match('/^[0-9]{10}$/', $billing_vat_number)) {
            wc_add_notice(__('<strong>Podany numer NIP jest niepoprawny.</strong> Wpisz polski numer NIP bez spacji i myślników.', 'woocommerce'), 'error');
        } else {
            // Wylicza sumę kontrolną
            $weights = [6, 5, 7, 2, 3, 4, 5, 6, 7];
            $sum = 0;
            for ($i = 0; $i < 9; $i++) {
                $sum += $billing_vat_number[$i] * $weights[$i];
            }
            $control_number = $sum % 11;

            // Sprawdza, czy suma kontrolna jest poprawna
            if ($control_number != $billing_vat_number[9]) {
                wc_add_notice(__('<strong>Podany numer NIP jest niepoprawny.</strong> Wpisz polski numer NIP bez spacji i myślników.', 'woocommerce'), 'error');
            } else {
                // Zapisuje przefiltrowaną wartość pola "billing_vat_number"
                $data['billing_vat_number'] = $billing_vat_number;
            }
        }
    }
    return $data;
}

// Dodajemy akcję czyszczenia sesji po zakończeniu zamówienia
add_action('woocommerce_thankyou', 'clear_vat_session');
function clear_vat_session() {
    WC()->session->__unset('billing_vat_on');
}

add_action('wp_ajax_update_vat_checkbox', 'update_vat_checkbox_session');
add_action('wp_ajax_nopriv_update_vat_checkbox', 'update_vat_checkbox_session');

function update_vat_checkbox_session() {
    WC()->session->set('billing_vat_on', ($_POST['state'] === '1'));
    wp_die();
}

I don’t know if it’s the best solution, but it works for now.

Would you like to get access to staging site to explore this?