How to validate an EU VAT number in PHP

PHP ships with SoapClient, which is enough to query VIES, the European Commission's VAT validation service. Here is working code and the traps to avoid.

Basic check with SoapClient

<?php
function checkVat(string $raw): array {
    $s = strtoupper(preg_replace('/[\s.\-]/', '', $raw));
    $country = substr($s, 0, 2) === 'GR' ? 'EL' : substr($s, 0, 2);
    $number  = substr($s, 2);

    $client = new SoapClient(
        'https://ec.europa.eu/taxation_customs/vies/checkVatService.wsdl',
        ['connection_timeout' => 10, 'exceptions' => true]
    );
    try {
        $r = $client->checkVat(['countryCode' => $country, 'vatNumber' => $number]);
    } catch (SoapFault $f) {
        // $f->faultstring: MS_MAX_CONCURRENT_REQ, MS_UNAVAILABLE, INVALID_INPUT...
        return ['error' => $f->faultstring];
    }
    return ['valid' => $r->valid, 'name' => $r->name ?? null, 'address' => $r->address ?? null];
}

Traps

• The WSDL is fetched on every new client unless soap.wsdl_cache_enabled is on. Keep it on, or reuse the client.
• Faults are normal. MS_MAX_CONCURRENT_REQ and MS_UNAVAILABLE mean a member state is busy or down. Do not refuse the order; validate again later. Details in this guide.
• Germany and Spain never return a name. Do not treat an empty name as a failure. See why.
• Validate the format first with a per-country regex (list of formats): it avoids most faults caused by typos.

WooCommerce and Laravel

Run the check when the customer enters the number, store the result and the date on the order or customer record, and cache it for 24 hours. In WooCommerce, hook woocommerce_after_checkout_validation; in Laravel, a custom validation rule that reads from cache before calling VIES.

The REST alternative

$ch = curl_init('https://vatline.p.rapidapi.com/v1/check');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['Content-Type: application/json',
                           'X-RapidAPI-Key: ' . $key,
                           'X-RapidAPI-Host: vatline.p.rapidapi.com'],
    CURLOPT_POSTFIELDS => json_encode(['vat_number' => 'FR40303265045']),
]);
$result = json_decode(curl_exec($ch), true);

Flat JSON, cached, with a retryable flag on every error.

Skip the plumbing. Vatline wraps VIES in a REST/JSON API with caching, retry hints and per-country circuit breakers. Free plan: 300 checks a month, no card. Read the docs or try a number now.