- var_dump: documentation ( source)
<?php
$nightStart = '23:00:00';
$nightEnd = '05:00:00';
$tripStart = new DateTime('2013-01-11 22:00:00');
$tripEnd = new DateTime('2013-01-12 00:00:00');
$now = new DateTime('now');
$today = $now->format('Y-m-d');
$nightTodayStart = new DateTime($today . $nightStart);
$nightFare = $tripEnd->diff($nightTodayStart);
var_dump($nightFare);
?>