Function that uses regular expressions to match against the various VAT formats required across the EU

regExVat.php

<?php
/**
 * This is a function that uses regular expressions to match against the various VAT formats required across the EU.
 * (tested, simple but effective)
 * 
 * TODO: Change country names to ISO codes?
 *
 * @param integer $country Country name
 * @param integer $vat_number VAT number to test e.g. GB123 4567 89
 * @return integer -1 if country not included OR 1 if the VAT Num matches for the country OR 0 if no match
*/
function checkVatNumber( $country, $vat_number ) {
    switch($country) {
        case 'Austria':
            $regex = '/^(AT){0,1}U[0-9]{8}$/i';
            break;
        case 'Belgium':
            $regex = '/^(BE){0,1}[0]{0,1}[0-9]{9}$/i';
            break;
        case 'Bulgaria':
            $regex = '/^(BG){0,1}[0-9]{9,10}$/i';
            break;
        case 'Cyprus':
            $regex = '/^(CY){0,1}[0-9]{8}[A-Z]$/i';
            break;
        case 'Czech Republic':
            $regex = '/^(CZ){0,1}[0-9]{8,10}$/i';
            break;
        case 'Denmark':
            $regex = '/^(DK){0,1}([0-9]{2}[\ ]{0,1}){3}[0-9]{2}$/i';
            break;
        case 'Estonia':
        case 'Germany':
        case 'Greece':
        case 'Portugal':
            $regex = '/^(EE|EL|DE|PT){0,1}[0-9]{9}$/i';
            break;
        case 'France':
            $regex = '/^(FR){0,1}[0-9A-Z]{2}[\ ]{0,1}[0-9]{9}$/i';
            break;
        case 'Finland':
        case 'Hungary':
        case 'Luxembourg':
        case 'Malta':
        case 'Slovenia':
            $regex = '/^(FI|HU|LU|MT|SI){0,1}[0-9]{8}$/i';
            break;
        case 'Ireland':
            $regex = '/^(IE){0,1}[0-9][0-9A-Z\+\*][0-9]{5}[A-Z]$/i';
            break;
        case 'Italy':
        case 'Latvia':
            $regex = '/^(IT|LV){0,1}[0-9]{11}$/i';
            break;
        case 'Lithuania':
            $regex = '/^(LT){0,1}([0-9]{9}|[0-9]{12})$/i';
            break;
        case 'Netherlands':
            $regex = '/^(NL){0,1}[0-9]{9}B[0-9]{2}$/i';
            break;
        case 'Poland':
        case 'Slovakia':
            $regex = '/^(PL|SK){0,1}[0-9]{10}$/i';
            break;
        case 'Romania':
            $regex = '/^(RO){0,1}[0-9]{2,10}$/i';
            break;
        case 'Sweden':
            $regex = '/^(SE){0,1}[0-9]{12}$/i';
            break;
        case 'Spain':
            $regex = '/^(ES){0,1}([0-9A-Z][0-9]{7}[A-Z])|([A-Z][0-9]{7}[0-9A-Z])$/i';
            break;
        case 'United Kingdom':
            $regex = '/^(GB){0,1}([1-9][0-9]{2}[\ ]{0,1}[0-9]{4}[\ ]{0,1}[0-9]{2})|([1-9][0-9]{2}[\ ]{0,1}[0-9]{4}[\ ]{0,1}[0-9]{2}[\ ]{0,1}[0-9]{3})|((GD|HA)[0-9]{3})$/i';
            break;
        default:
            return -1;
            break;
    }
   
    return preg_match($regex, $vat_number);
}
?>