How to get the year, month, day, hour, minute and second between a specified time period in PHP

Class Utils {
     /**
	 * format MySQL DateTime (YYYY-MM-DD hh:mm:ss) 把mysql中查找出来的数据格式转换成时间秒数
	 * @param string $datetime
	 */
	public function fmDatetime($datetime) {
	  $year = substr($datetime,0,4);
	  $month = substr($datetime,5,2);
	  $day = substr($datetime,8,2);
	  $hour = substr($datetime,11,2);
	  $min = substr($datetime,14,2);
	  $sec = substr($datetime,17,2);
	  return mktime($hour,$min,$sec,$month,$day,0+$year);
	}
	/**
	 * 
	 * 根据俩个时间获取俩个时间的 包含的 年，月数，天数，小时，分钟，秒
	 * @param String $start
	 * @param String $end
	 * @return ArrayObject 
	 */
	 private function diffDateTime($DateStart,$DateEnd){
		$rs = array();
		
		$sYear = substr($DateStart,0,4);
		$eYear = substr($DateEnd,0,4);
		
		$sMonth = substr($DateStart,5,2);
		$eMonth = substr($DateEnd,5,2);
		
		$sDay = substr($DateStart,8,2);
		$eDay = substr($DateEnd,8,2);
		
		$startTime = $this->fmDatetime($DateStart);
		$endTime = $this->fmDatetime($DateEnd);
		$dis = $endTime-$startTime;//得到俩个时间的秒数
		$d = ceil($dis/(24*60*60));//得到天数
		$rs['day'] = $d;//天数
		$rs['hour'] = ceil($dis/(60*60));//小时
		$rs['minute'] = ceil($dis/60);//分钟
		$rs['second'] = $dis;//秒数
		$rs['week'] = ceil($d/7);//周
		
		$tem = ($eYear-$sYear)*12;//月份
		$tem1 = $eYear-$sYear;//年
		if($eMonth-$sMonth<0){//月份相减为负
			$tem +=($eMonth-$sMonth);
		}else if($eMonth==$sMonth){//月份相同
			if($eDay-$sDay>=0){
				$tem ++;
				$tem1++;
			}
		}else if($eMonth-$sMonth>0){//月份相减正负
			$tem1++;
			if($eDay-$sDay>=0){//且日期相减为正数
				$tem +=($eMonth-$sMonth)+1;
			}else{
				$tem +=($eMonth-$sMonth);
			}
		}
		$rs[&#39;month&#39;] = $tem;
		$rs[&#39;year&#39;] = $tem1;
		
		return $rs;
	}
}