How to return the difference in hours between two dates? [duplicate]

You can use the DateTime::diff to know the interval between two dates, to know the difference in hours, you get the difference in days and multiply by 24 .

$datatime1 = new DateTime('2015/04/15 00:00:00');
$datatime2 = new DateTime('2015/05/16 00:00:00');

$data1  = $datatime1->format('Y-m-d H:i:s');
$data2  = $datatime2->format('Y-m-d H:i:s');

$diff = $datatime1->diff($datatime2);
$horas = $diff->h + ($diff->days * 24);

echo "A diferença de horas entre {$data1} e {$data2} é {$horas} horas";

Exemplo

<?php
$date1 = new DateTime("now");
$date2 = new DateTime("tomorrow");

$interval = date_diff($date1, $date2);