FormValidatorUsername.inc.php

<?php
 
import('lib.pkp.classes.form.validation.FormValidator');
 
class FormValidatorUsername extends FormValidator {
   function __construct(&$form, $field, $type, $message) {
      import('lib.pkp.classes.validation.ValidatorRegExp');
      parent::__construct(
         $form, $field, $type, $message,
         new ValidatorRegExp('/^[a-z0-9]+([\-_][a-z0-9]+)*$/')
      );
   }
}