php实现简单的日历类

[PHP]代码

<?php  class calendar{      private $year;      private $month;      private $day_week;        function __construct(){          $this->year=isset($_GET['year']) ? $_GET['year'] : date("Y");          $this->month=isset($_GET['month']) ? $_GET['month'] : date("m");          $this->day_week=date("w", mktime(0, 0, 0, $this->month, 1, $this->year));      }        private function xianDate(){          echo "<tr>";          echo "<td><a href='".$this->nextyear($this->year, $this->month)."'>"."<<<"."</a></td>";          echo "<td><a href='".$this->nextmonth($this->month, $this->year)."'>"."<<"."</td>";          echo "<td colspan='3'>".$this->year."年".$this->month."月</td>";          echo "<td><a href='".$this->aftermonth($this->month, $this->year)."'>".">>"."</td>";          echo "<td><a href='".$this->afteryear($this->year, $this->month)."'>".">>>"."</a></td>";          echo "</tr>";      }        private function weeks(){          $weeks=array("日", "一", "二", "三", "四", "五", "六");          echo "<tr>";          foreach($weeks as $value){              echo "<th>".$value."</th>";          }          echo "</tr>";      }        private function days(){          echo "<tr>";          for($i=0; $i<$this->day_week; $i++){              echo "<td> </td>";          }          for($j=1; $j <= date("t", mktime(0, 0, 0, $this->month, 1, $this->year)); $j++){              $i++;              if($j == date("d")){                  echo "<td class='fontb'>".$j."</td>";              }else{                  echo "<td>".$j."</td>";              }              if($i%7 == 0){                  echo "</tr>";              }          }          while($i%7 != 0){              echo "<td> </td>";              $i++;          }      }        private function nextyear($year, $month){          if($year == 1970){              $year=1970;          }else{              $year--;          }          return "?year=".$year."&month=".$month;      }        private function afteryear($year, $month){          if($year == 2038){              $year=2038;          }else{              $year++;          }          return "?year=".$year."&month=".$month;      }        private function nextmonth($month, $year){          if($month == 1){              $year--;              $month=12;          }else{              $month--;          }          return "?year=".$year."&month=".$month;      }        private function aftermonth($month, $year){          if($month == 12){              $year++;              $month=1;          }else{              $month++;          }          return "?year=".$year."&month=".$month;      }        public function out(){          echo "<table align='center'>";          $this->xianDate();          $this->weeks();          $this->days();          echo "</table>";      }  }    ?>