PHP封装时间类

开发中经常用到时间的一些操作，比如昨天，今天，前天，近七天，一周等等。

class time{
        private $year;//年
        private $month;//月
        private $day;//天
        private $hour;//小时
        private $minute;//分钟
        private $second;//秒
        private $microtime;//毫秒
        private $weekday;//星期
        private $longDate;//完整的时间格式
        private $diffTime;//两个时间的差值
        //返回年份 time：时间格式为时间 2018-8-21
        function getyear($time="",$type=""){
                if($time==""){
                        $time=time();
                }
                if($type==1){
                        return $this->year=date("y",$time); //返回两位的年份 18
                }else{
                        return $this->year=date("Y",$time); //返回四位的年份 2018
                }
        }
        //返回当前时间的月份 time：时间格式为时间 2018-8-21
        function getmonth($time="",$type=""){
                if($time==""){
                        $time=time();
                }
                switch($type){
                        case 1:$this->month=date("n",$time);//返回格式 8
                        break;
                        case 2:$this->month=date("m",$time);//返回格式 08
                        break;
                        case 3:$this->month=date("M",$time);//返回格式 Aug
                        break;
                        case 4:$this->month=date("F",$time);//返回格式 August
                        break;
                        default:$this->month=date("n",$time);
                }
                return $this->month; 
        }
        //返回当前时间的天数 time：时间格式为时间 2018-8-21 
        function getday($time="",$type=""){
                if($time==""){
                        $time=time();
                }
                if($type==1){
                        $this->day=date("d",$time);//返回格式 21
                }else{
                        $this->day=date("j",$time);//返回格式 21
                }
                return $this->day;
        }
        //返回当前时间的小时  2018-08-21 1:19:21 20:19:21 
        function gethour($time="",$type=""){
                if($time==""){
                        $time=time();
                } 
                switch($type){
                        case 1:$this->hour=date("H",$time);//格式： 1 20
                        break;
                        case 2:$this->hour=date("h",$time);//格式  01 08
                        break;
                        case 3:$this->hour=date("G",$time);//格式  1 20
                        break;
                        case 4:$this->hour=date("g",$time);//格式  1 8
                        break; 
                        default :$this->hour=date("H",$time);
                }
                return $this->hour;
        }
        //返回当前时间的分钟数 1:9:18  
        function getminute($time="",$type=""){
                if($time==""){
                        $time=time();
                }
                $this->minute=date("i",$time); //格式  09
                return $this->minute;
        }
        //返回当前时间的秒数  20:19:01
        function getsecond($time="",$type=""){
                if($time==""){
                        $time=time();
                }
                $this->second=date("s",$time); //格式  01
                return $this->second;
        }
        //返回当前时间的星期数 
        function getweekday($time="",$type=""){
                if($time==""){
                        $time=time(); 
                }
                if($type==1){
                        $this->weekday=date("D",$time);//格式  Sun
                }else if($type==2){
                        $this->weekday=date("l",$time); //格式 Sunday
                }else{
                        $this->weekday=date("w",$time);//格式 数字表示 0--6
                }
                return $this->weekday;
        }
        //比较两个时间的大小 格式 2018-8-21 8:4:3  
        function compare($time1,$time2){
                $time1=strtotime($time1);
                $time2=strtotime($time2);
                if($time1>=$time2){  //第一个时间大于等于第二个时间 返回1 否则返回0
                        return 1;
                }else{
                        return -1;
                }
        }
        //比较两个时间的差值
        function diffdate($time1="",$time2=""){
                //echo $time1.'------'.$time2.'<br>';
                if($time1==""){
                        $time1=date("Y-m-d H:i:s"); 
                }
                if($time2==""){ 
                        $time2=date("Y-m-d H:i:s"); 
                }
                $date1=strtotime($time1);
                $date2=strtotime($time2);
                if($date1>$date2){
                        $diff=$date1-$date2; 
                }else{
                        $diff=$date2-$date1;
                }
                if($diff>=0){
                        $day=floor($diff/86400);
                        $hour=floor(($diff%86400)/3600);
                        $minute=floor(($diff%3600)/60);
                        $second=floor(($diff%60));
                        $this->diffTime='相差'.$day.'天'.$hour.'小时'.$minute.'分钟'.$second.'秒'; 
                }
                return $this->diffTime;
        }
        //返回 X年X月X日
        function buildDate($time="",$type=""){
                if($type==1){   
                        $this->longDate = $this->getyear($time) . '年' . $this->getmonth($time) . '月' . $this->getday($time) . '日';  
                }else{
                        $this->longDate = $this->getyear($time) . '年' . $this->getmonth($time) . '月' . $this->getday($time) . '日'.$this->gethour($time).':'.$this->getminute($time).':'.$this->getsecond($time);  
                }
                return $this->longDate;  
        }
}

实例化这个对象

   $time_var = "2018-08-21";
   $obj = new time();
   $year = $obj->getyear($time_var);

   echo($year);