- date: documentation ( source)
<?php
$d1 = new DateTime('2015-06-30 23:59:59');
$d2 = new DateTime('2015-06-30 23:59:60');
echo $d1->format('U');
echo PHP_EOL;
echo $d1->format('Y-m-d H:i:s');
echo PHP_EOL;
echo $d2->format('U');
echo PHP_EOL;
echo $d2->format('Y-m-d H:i:s');
echo PHP_EOL;
echo date('r', 1435701600);