- var_dump: documentation ( source)
<?php
$dateTime = new DateTime();
$midnight = new DateTimeImmutable($dateTime->format('Ymd'), $dateTime->getTimezone());
var_dump($dateTime->format(DATE_ISO8601));
var_dump($dateTime->getTimezone());
var_dump($midnight->format(DATE_ISO8601));
var_dump($midnight->getTimezone());