ValidatorISSN.inc.php

<?php
 
import('lib.pkp.classes.validation.Validator');
import('lib.pkp.classes.validation.ValidatorFactory');
 
class ValidatorISSN extends Validator {
   function isValid($value) {
      $validator = \ValidatorFactory::make(
         ['value' => $value],
         ['value' => ['required', 'issn']]
      );
 
      return $validator->passes();
   }
}