<?php

define("SECOND", 1);
define("MINUTE", 60*SECOND);
define("HOUR", 60*MINUTE);
define("DAY", 24*HOUR);
define("YEAR", 365*DAY);
define("MONTH", YEAR/12);

function datediff($start, $end)
{

        $diff = strtotime($end) - strtotime($start);

        $periods = array("year" => YEAR, 
                         "month" => MONTH, 
                         "day" => DAY, 
                         "hour" => HOUR, 
                         "minute" => MINUTE,
                         "second" => SECOND);

        foreach ($periods as $period => $duration) {
                $tmp = floor($diff/$duration);
                $diff%=$duration;

                $output.=$tmp." ".ucwords(strtolower($period)).($tmp!=1 ? 's' : '');
                if ($period != 'second') $output.=", ";
        }

        return $output;
}

echo datediff('2007-01-05 12:53:17','2008-03-28 17:57:12');
?>