calculate (year, month, date) with PHP DateDiff Function

Today, I am really stress with the calculate the number of year, month, date which calcuated from the expired date with the current date, that so, I have search by google then making decision on the following style to improve my problem, and I am still on hesitat it yet, coz it's not fully requirement which I need, but this below function also the rest of solving problem with date... By this point, it show the number of year, or month, or date, .....

function datediff($interval, $datefrom, $dateto, $using_timestamps = false) {
/*
$interval can be:
yyyy - Number of full years
q - Number of full quarters
m - Number of full months
y - Difference between day numbers
(eg 1st Jan 2004 is "1", the first day. 2nd Feb 2003 is "33". The datediff is "-32".)
d - Number of full days
w - Number of full weekdays
ww - Number of full weeks
h - Number of full hours
n - Number of full minutes
s - Number of full seconds (default)
*/

if (!$using_timestamps) {
$datefrom = strtotime($datefrom, 0);
$dateto = strtotime($dateto, 0);
}
$difference = $dateto - $datefrom; // Difference in seconds

switch($interval) {

case 'yyyy': // Number of full years

$years_difference = floor($difference / 31536000);
if (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom), date("j", $datefrom), date("Y", $datefrom)+$years_difference) > $dateto) {
$years_difference--;
}
if (mktime(date("H", $dateto), date("i", $dateto), date("s", $dateto), date("n", $dateto), date("j", $dateto), date("Y", $dateto)-($years_difference+1)) > $datefrom) {
$years_difference++;
}
$datediff = $years_difference;
break;

case "q": // Number of full quarters

$quarters_difference = floor($difference / 8035200);
while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($quarters_difference*3), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
$months_difference++;
}
$quarters_difference--;
$datediff = $quarters_difference;
break;

case "m": // Number of full months

$months_difference = floor($difference / 2678400);
while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($months_difference), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
$months_difference++;
}
$months_difference--;
$datediff = $months_difference;
break;

case 'y': // Difference between day numbers

$datediff = date("z", $dateto) - date("z", $datefrom);
break;

case "d": // Number of full days

$datediff = floor($difference / 86400);
break;

case "w": // Number of full weekdays

$days_difference = floor($difference / 86400);
$weeks_difference = floor($days_difference / 7); // Complete weeks
$first_day = date("w", $datefrom);
$days_remainder = floor($days_difference % 7);
$odd_days = $first_day + $days_remainder; // Do we have a Saturday or Sunday in the remainder?
if ($odd_days > 7) { // Sunday
$days_remainder--;
}
if ($odd_days > 6) { // Saturday
$days_remainder--;
}
$datediff = ($weeks_difference * 5) + $days_remainder;
break;

case "ww": // Number of full weeks

$datediff = floor($difference / 604800);
break;

case "h": // Number of full hours

$datediff = floor($difference / 3600);
break;

case "n": // Number of full minutes

$datediff = floor($difference / 60);
break;

default: // Number of full seconds (default)

$datediff = $difference;
break;
}

return $datediff;

}

?>

reference : http://www.addedbytes.com/php/php-datediff-function/