$startdate="2010-12-11 11:40:00";
$enddate="2012-12-12 11:45:09";
$date=floor((strtotime($enddate)-strtotime($startdate))/86400);
$hour=floor((strtotime($enddate)-strtotime($startdate))/86400/3600);
$minute=floor((strtotime($enddate)-strtotime($startdate))/86400/60);
$second=floor((strtotime($enddate)-strtotime($startdate))/86400/60);
echo $date."天<br>";
echo $hour."小时<br>";
echo $minute."分钟<br>";
echo $second."秒<br>";

/** 
 +---------------------------------------------------------- 
 * 功能：计算两个日期相差 年 月 日 
 +---------------------------------------------------------- 
 * @param date   $date1 起始日期 
 * @param date   $date2 截止日期日期 
 +---------------------------------------------------------- 
 * @return array       
 +---------------------------------------------------------- 
 */
function DiffDate($date1, $date2) { 
  if (strtotime($date1) > strtotime($date2)) { 
    $ymd = $date2; 
    $date2 = $date1; 
    $date1 = $ymd; 
  } 
  list($y1, $m1, $d1) = explode('-', $date1); 
  list($y2, $m2, $d2) = explode('-', $date2); 
  $y = $m = $d = $_m = 0; 
  $math = ($y2 - $y1) * 12 + $m2 - $m1; 
  $y = round($math / 12); 
  $m = intval($math % 12); 
  $d = (mktime(0, 0, 0, $m2, $d2, $y2) - mktime(0, 0, 0, $m2, $d1, $y2)) / 86400; 
  if ($d < 0) { 
    $m -= 1; 
    $d += date('j', mktime(0, 0, 0, $m2, 0, $y2)); 
  } 
  $m < 0 && $y -= 1; 
  return array($y, $m, $d); 
}

{php
$startdate="2010-12-11 11:40:00";
$enddate="2012-12-12 11:45:09";
$date=floor((strtotime($enddate)-strtotime($startdate))/86400);
$year = cell($date / 365);
}

{php echo date("Y") - date("Y", $_aaa);}