easyappointments/src/engine/Types/UnsignedInteger.php

<?php 

/* ----------------------------------------------------------------------------
 * Easy!Appointments - Open Source Web Scheduler
 *
 * @package     EasyAppointments
 * @author      A.Tselegidis <alextselegidis@gmail.com>
 * @copyright   Copyright (c) 2013 - 2017, Alex Tselegidis
 * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
 * @link        http://easyappointments.org
 * @since       v1.2.0
 * ---------------------------------------------------------------------------- */

namespace EA\Engine\Types; 

class UnsignedInteger extends Integer {
    protected function _validate($value) {
        return parent::_validate($value) && $value > -1; 
    }   
}