- date: documentation ( source)
- strtotime: documentation ( source)
<?php
echo date('H:i:s Y-m-d',strtotime("midnight today"));
echo "[" . new DateTime("2015-11-05 16:00:00") - new DateTime("midnight today") . "]\n";
echo "[" . new DateTime("2015-11-04 16:00:00") - new DateTime("midnight today") . "]\n";