General Date Convertor and Calculator (Simple)

function mod_date($date_in,$format_in,$y,$m,$d,$h,$i,$s,$format_out){
/*	
	Written by Alan Davies, 2009
	============================
 
	PARAMETERS
	==========
	$date_in: 		STRING date or datetime in standard uk, unix or us format.
	$format_in: 	STRING u = unix, d = uk date, a = usa date
	$y:				Year (INTEGER), negative, positive or 0
	$m:				Month (INTEGER), negative, positive or 0
	$d:				Day (INTEGER), negative, positive or 0
	$h:				Hour (INTEGER), negative, positive or 0
	$i:				Minute (INTEGER), negative, positive or 0
	$s:				Second (INTEGER), negative, positive or 0
	$format_out: 	STRING u = unix, d = uk date, a = usa date, 
					ut = unix date + time, dt = uk date + time, at = usa date + time
 
	Example uses
	============
	1. 	converting a date from uk -> unix -> us and viceversa
	 	mod_date('23/11/2009','d',0,0,0,0,0,0,'u') would change uk date to unix
 
	2. 	adding or subtracting time to date
		mod_date('23/11/2009 13:00:00','d',1,0,0,-3,0,0,'ut') add one year, subtract 3 hours and place in unix format [2010-11-23 10:00:00]
		the function also corrects overflows (e.g. adding 13 months will actually add i year and 1 month)
*/
 
 
	$date_in = trim($date_in);
	$time_element = strstr($date_in," ");
	if($time_element){
		$datetime = explode(" ",$date_in);
		$date_aspect = $datetime[0];
		$time_aspect = $datetime[1]; 
		if(strstr($time_aspect,":")){
			$time_parts = explode(":",$time_aspect);
			$dh = $time_parts[0];settype($dh,"integer");
			$di = $time_parts[1];settype($dh,"integer");
			if(isset($time_parts[2])){
				$ds = $time_parts[2];settype($dh,"integer");
			}
		}
	}else{
		$date_aspect = $date_in;
	}
	if(!isset($dh) || $dh == "" || !is_int($dh))$dh = 0;
	if(!isset($di) || $di == "" || !is_int($di))$di = 0;
	if(!isset($ds) || $ds == "" || !is_int($ds))$ds = 0;
 
	if(strstr($date_aspect,"/"))$date_parts = explode("/",$date_aspect);
	if(strstr($date_aspect,"-"))$date_parts = explode("-",$date_aspect);
	switch($format_in){
		case 'd':
			$dd = $date_parts[0];
			$dm = $date_parts[1];
			$dy = $date_parts[2];
			break;
		case 'u':
			$dd = $date_parts[2];$dm = $date_parts[1];$dy = $date_parts[0];
			break;
		case 'a':
			$dd = $date_parts[1];$dm = $date_parts[0];$dy = $date_parts[2];
			break;
		default:
			$error_msg = "You must provide a proper format for the input date: chose from 'u' (unix date/time), 'd' (UK date/time), 'a' (US date/time).";
			return $error_msg;
			break;
	}
 
	$date = mktime($dh + $h,$di + $i,$ds + $s,$dm + $m,$dd + $d, $dy + $y);
 
	switch($format_out){
		case 'd':
			$my_date = date('d/m/Y',$date);
			break;
		case 'u':
			$my_date = date('Y-m-d',$date);
			break;
		case 'a':
			$my_date = date('m/d/Y',$date);
			break;
		case 'dt':
			$my_date = date('d/m/Y H:i:s',$date);
			break;
		case 'ut':
			$my_date = date('Y-m-d H:i:s',$date);
			break;
		case 'at':
			$my_date = date('m/d/Y H:i:s',$date);
			break;
		default:
			$error_msg = "You must provide a proper format for output: chose from 'u' (unix date), 'd' (UK date), 'a' (US date), 'ut' (unix datetime), 'dt' (UK datetime), 'at' (US datetime).";
			return $error_msg;
			break;
	}
	return $my_date;
}