PHP Calendar Class Tutorial with Full Implementation

When handling dates and times in web applications, a reusable calendar component is essential, not only for displaying the current date but also for tasks such as scheduling and note‑taking.

The article defines a Calendar class in calendar.class.php, which stores the year, month, start weekday and total days, provides methods to generate the week header, day cells, navigation links for previous/next month and year, and renders the whole calendar as an HTML table.

Key methods include __construct() for initializing properties from URL parameters, __toString() to output the table, weeksList(), daysList(), and helper functions prevYear(), prevMonth(), nextYear(), nextMonth(), and changeDate() for building the navigation form.

A simple front‑end script loads the class, echoes a new Calendar instance, and applies basic CSS to style the table, producing a functional calendar view as shown in the screenshot.

<?php
/*  calendar.class.php日历类
   声明一个日历类，名称为Calendar，用来显示可以设置日期的日历
 */
class Calendar{
  private $year;//当前的年
  private $month;//当前的月
  private $start_weekday;//当月的第一天对应的是周几，作为当月遍历日期的开始
  private $days;//当前月的总天数

  /** 构造方法，初始化一些属性 */
  function __construct(){
    $this->year = isset($_GET["year"]) ? $_GET["year"] :date("Y") ;
    $this->month = isset($_GET["month"]) ? $_GET["month"] :date("m") ;
    $this->start_weekday = date("w",mktime(0, 0, 0, $this->month, 1, $this->year));
    $this->days = date("t",mktime(0, 0, 0, $this->month, 1, $this->year));
  }
  /** 打印整个日历 */
  function __toString(){
    $out .= '<table align="center">';
    $out .= $this->changeDate();
    $out .= $this->weeksList();
    $out .= $this->daysList();
    $out .= '</table>';
    return $out;
  }
  /** 输出周列表 */
  private function weeksList(){
    $week = array ('日','一','二','三','四','五','六');
    $out .= '<tr>';
    for($i = 0; $i < count($week); $i++){
      $out .= '<th class="fontb">' . $week [$i]. '</th>';
    }
    $out .= '</tr>';
    return $out;
  }
  /** 输出日列表 */
  private function daysList(){
    $out .= '<tr>';
    for($j = 0; $j < $this->start_weekday; $j++){
      $out .= '<td> </td>';
    }
    for($k = 1; $k <= $this->days; $k++){
      $j++;
      if($k == date('d')){
        $out .= '<td class="fontb">'.$k.'</td>';
      } else {
        $out .= '<td>'.$k.'</td>';
      }
      if($j%7 == 0){
        $out .= '</tr><tr>';
      }
    }
    while ($j%7 != 0) {
      $out .= '<td> </td>';
      $j++;
    }
    $out .= '</tr>';
    return $out;
  }
  private function prevYear($year, $month){
    $year = $year-1;
    if ($year < 1970){ $year = 1970; }
    return "year={$year}&month={$month}";
  }
  private function prevMonth($year, $month){
    if($month== 1){
      $year = $year -1;
      if($year < 1970){ $year = 1970; }
      $month = 12;
    } else {
      $month--;
    }
    return "year={$year}&month={$month}";
  }
  private function nextYear($year, $month){
    $year = $year+1;
    if ($year> 2038){ $year=2038; }
    return "year={$year}&month={$month}";
  }
  private function nextMonth($year, $month){
    if($month == 12){
      $year++;
      if($year> 2038){ $year = 2038; }
      $month = 1;
    } else {
      $month++;
    }
    return "year={$year}&month={$month}";
  }
  private function changeDate($url='index.php'){
    $out .= '<tr>';
    $out .= '<td><a href="'.$url.'?'.$this->prevYear($this->year,$this->month).'"><<</a></td>';
    $out .= '<td><a href="'.$url.'?'.$this->prevMonth($this->year,$this->month).'"<</a> </td>';
    $out .= '<td colspan="3">';
    $out .= '<form>';
    $out .= '<select name="year" onchange="window.location=\''.$url.'?year=\'+this.options[selectedIndex].value+\'&month='.$this->month.'\'">';
    for($sy=1970; $sy <= 2038; $sy++){
      $selected = ($sy==$this->year) ? "selected" : "";
      $out .= '<option '.$selected.' value="'.$sy.'">'.$sy.'</option>';
    }
    $out .= '</select>';
    $out .= '<select name="month" onchange="window.location=\''.$url.'?year='.$this->year.'&month=\'+this.options[selectedIndex].value">';
    for ($sm=1; $sm <=12; $sm++){
      $selected1 = ($sm==$this->month) ? "selected" : "";
      $out .= '<option '.$selected1.' value="'.$sm.'">'.$sm.'</option>';
    }
    $out .= '</select>';
    $out .= '</form>';
    $out .= '</td>';
    $out .= '<td> <a href="'.$url.'?'.$this->nextMonth($this->year,$this->month).'">></a></td>';
    $out .= '<td> <a href="'.$url.'?'.$this->nextYear($this->year,$this->month).'">>></a></td>';
    $out .= '</tr>';
    return $out;
  }
}
?>

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>日历示例</title>
<style>
table{ border: 1px solid #050; }
.fontb{ color:white;background:blue; }
th { width: 30px; }
td,th { height: 30px;text-align:center; }
form { margin:0px;padding:0px; }
</style>
</head>
<body>
<?php
require 'calendar.class.php';
echo new Calendar;
?>
</body>
</html>