- var_dump: documentation ( source)
- timezone_name_from_abbr: documentation ( source)
<?php
$_REQUEST['tzo'] = 720;
$orderdate = new DateTime('2005-10-10');
$timeZoneName = timezone_name_from_abbr("", (intval($_REQUEST['tzo'])/60)*3600, 1);
$orderdate->setTimezone(new DateTimezone($timeZoneName));
var_dump($orderdate->format('c e T'));
$orderdate->setTimezone(new DateTimeZone('CET'));
var_dump($orderdate->format('c e T'));