Difference in hours between two dates.

date-diff.php

<?php
$now = new DateTime('now', new DateTimeZone('America/Mexico_City'));

$twoHoursAgo = clone $now;
$twoHoursAgo = $twoHoursAgo->sub(new DateInterval('PT2H'));

$diff = $now->diff($twoHoursAgo);

echo $diff->format("%H hours\n");