- var_dump: documentation ( source)
<?php
$now = new DateTime();
$twoDaysAgo1 = new DateTime('-2 days');
$twoDaysAgo2 = new DateTime('-172800 seconds');
$twoDaysAgo3 = new DateTime('@' . ($now->getTimestamp() - 172800));
var_dump($twoDaysAgo1->getTimestamp());
var_dump($twoDaysAgo2->getTimestamp());
var_dump($twoDaysAgo3->getTimestamp());