<?php
$january = new DateTime('2010-01-01');
$february = new DateTime('2010-02-10');
$interval = $february->diff($january);
// %a will output the total number of days.
echo $interval->format('%a total days')."\n";
// While %d will only output the number of days not already covered by the
// month.
echo $interval->format('%m month, %d days');