A simple solution to count days between 2 dates is using DateTime method since php 5.3

function getDaysBetweenDates($from,$to,$addLastDay = false){
	$d1 = new \DateTime($from);
	$d2 = new \DateTime($to);
	if($addLastDay){
		$d2->add(new \DateInterval('P1D'));
	}
	return $d1 -> diff($d2)->days;
}
echo getDaysBetweenDates('2013-03-01','2013-03-11');
//10
echo getDaysBetweenDates('2013-03-01','2013-03-11',true);
//11

If you need to count the last day too , just pass third parameter – true.