LicensePlateValidator.php

<?php

namespace Foo\Validator;

use Zend\Validator\ValidatorInterface;

final class LicensePlateValidator implements ValidatorInterface
{
    const FORMATS = [
        // Germany (Total Length: 8 characters excluding spaces, No leading zeros, can end in E or H)
        '/^(?=.{5,10}$|.{5,10}(?:H|E)$)[A-ZÖÜÄ]{1,3} [A-Z]{1,2} [1-9][0-9]{0,3}(?: H| E){0,1}$/',
        // Austria (Total Length: 7 characters excluding spaces, No leading zeros, no Q in 2nd letter block
        '/^(?=.{5,9}$)[A-Z]{1,2} (?:([1-9][0-9]{0,4}) ([A-PR-Z]{1,5})|(?2) (?1))$/',
    ];
    /** @var array */
    private $messages;

    public function isValid($value): bool
    {
        foreach (self::FORMATS as $format) {
            if (preg_match($format, $value) === 1) {
                return true;
            }
        }

        $this->messages[] = 'Invalid license plate format. Only numbers, letters and spaces are allowed';

        return false;
    }

    public function getMessages(): array
    {
        return $this->messages;
    }
}