VIES VAT custom validation for Wordpress Ultimate Members field

um_vies_vat_validation.php

<?php

/**
 * This is a custom validation for Ultimate Members Wordpress plugin
 * Apply custom validation to VAT field with the name vat_number
 * It requires also a country field
 * This expects a user to enter a VAT Number in the following format:
 * EL-123456789
 *
 * Add um_custom_vat_validation on Custom Action field
 *
 * @author sirtimid.com
 */
if(!function_exists('um_custom_vat_validation')){
	function um_custom_vat_validation( $args ) {
		global $ultimatemember;

		$eu_countries = array(
			'Austria','Belgium','Bulgaria','Croatia','Cyprus','Czech Republic','Denmark',
			'Estonia','Finland','France','Germany','Greece','Hungary','Ireland','Italy',
			'Latvia','Lithuania','Luxembourg','Malta','Netherlands','Poland','Portugal',
			'Romania','Slovakia','Slovenia','Spain','Sweden','United Kingdom'
		);

		// check if vat_number is set and the country is in Europe
		if ( isset($args['vat_number']) && isset($args['country']) && in_array($args['country'], $eu_countries) ) {
			$vat = explode('-', $args['vat_number']);
			$vies = check_VIES_VAT($countryCode, $vatNumber);
			if(!$vies['valid']){
				$ultimatemember->form->add_error( 'vat_number', 'Your VAT Number is not valid.' );
			}
		}
	}
	add_action('um_submit_form_errors_hook_','um_custom_vat_validation', 999, 1);
}

/**
 * VIES VAT number validation
 * Based on http://stackoverflow.com/a/29955950
 *
 * @author Eugen Mihailescu
 *
 * @param string $countryCode
 * @param string $vatNumber
 * @param int $timeout
 *
 * @return array
 *
 * Array
 * (
 *     [countryCode] => EL
 *     [vatNumber] => 111111111
 *     [requestDate] => 2017-01-01+00:00
 *     [valid] => true
 *     [name] => JOHN DOE
 *     [address] => STREET No POSTAL_CODE - CITY
 * )
 */
if(!function_exists('check_VIES_VAT')){
	function check_VIES_VAT($countryCode, $vatNumber, $timeout = 30) {
		$response = array ();
		$pattern = '/<(%s).*?>([\s\S]*)<\/\1/';
		$keys = array (
			'countryCode',
			'vatNumber',
			'requestDate',
			'valid',
			'name',
			'address'
			);

		$content = "<s11:Envelope xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'>
									<s11:Body>
										<tns1:checkVat xmlns:tns1='urn:ec.europa.eu:taxud:vies:services:checkVat:types'>
											<tns1:countryCode>%s</tns1:countryCode>
											<tns1:vatNumber>%s</tns1:vatNumber>
										</tns1:checkVat>
									</s11:Body>
								</s11:Envelope>";

		$opts = array (
			'http' => array (
				'method' => 'POST',
				'header' => "Content-Type: text/xml; charset=utf-8; SOAPAction: checkVatService",
				'content' => sprintf ( $content, $countryCode, $vatNumber ),
				'timeout' => $timeout
			)
		);

		$ctx = stream_context_create($opts);
		$result = file_get_contents('http://ec.europa.eu/taxation_customs/vies/services/checkVatService', false, $ctx );

		if(preg_match ( sprintf ( $pattern, 'checkVatResponse' ), $result, $matches )) {
			foreach ($keys as $key){
				preg_match ( sprintf ( $pattern, $key ), $matches [2], $value ) && $response [$key] = $value [2];
			}
		}
		return $response;
	}
}

?>