PHP 計算Date類型的差值

<?php
class timeDiffer{

    function getTimeDiffer($startdate){
		$enddate=date('Y-m-d H:i:s',time());
		$date=floor((strtotime($enddate)-strtotime($startdate))/86400);
          $hour=floor(((strtotime($enddate)-strtotime($startdate))%86400)/3600%24);
          $minute=floor(((strtotime($enddate)-strtotime($startdate))%86400)/60%60);
          $second=floor((strtotime($enddate)-strtotime($startdate))%86400%60);
		
		$differTime = "";
		if((!empty($date))||$date!=null||$date!=0){
			$differTime =$differTime.$date."天";
		}
		if((!empty($hour))||$hour!=null||$hour!=0){
			$differTime =$differTime.$hour."小時";
		}
		if((!empty($minute))||$minute!=null||$minute!=0){
			$differTime =$differTime.$minute."分鐘";
		}
                if((!empty($second))||$second!=null||$second!=0){
			$differTime =$differTime.$second."分鐘";
		}


                // echo $date."天<br>";
                // echo $hour."小時<br>";
                // echo $minute."分鐘<br>";
                // echo $second."秒<br>";

                return $differTime;
     }
}
?>