- var_dump: documentation ( source)
<?php
$dateTime = new DateTimeImmutable('2014-10-26 01:00:00', new DateTimeZone('Europe/Berlin'));
var_dump($dateTime->format(DATE_ISO8601));
$test = $dateTime->modify('+61 minutes');
var_dump($test->format(DATE_ISO8601));
$test = $dateTime->modify('+121 minutes');
var_dump($test->format(DATE_ISO8601));