- date_diff: documentation ( source)
- var_dump: documentation ( source)
<?php
$a = new DateTime('2000-01-01');
$b = new DateTime('2010-01-01');
$diff = date_diff($a, $b);
echo '$a=', $a->format('Y-m-d H:i:s'), "\n";
echo '$b=', $b->format('Y-m-d H:i:s'), "\n";
var_dump($diff);