如何使用PHP实现微信小程序中的日历功能

//获取当前日期的年份和月份
$year = isset($_POST['year']) ? $_POST['year'] : date('Y');
$month = isset($_POST['month']) ? $_POST['month'] : date('m');

//计算当月的天数和第一天的星期数
$days = date('t', strtotime($year . '-' . $month . '-01'));
$firstWeekday = date('w', strtotime($year . '-' . $month . '-01'));

<table>
  <thead>
    <tr>
      <th>日</th>
      <th>一</th>
      <th>二</th>
      <th>三</th>
      <th>四</th>
      <th>五</th>
      <th>六</th>
    </tr>
  </thead>
  <tbody>
    <?php
      $day = 1;
      $weekday = $firstWeekday;
      $flag = true;
      while ($flag) {
        echo '<tr>';
        for ($i = 0; $i < 7; $i++) {
          if ($day > $days) {
            $flag = false;
            break;
          }
          if ($i < $weekday) {
            echo '<td></td>';
          } else {
            echo '<td>' . $day . '</td>';
            $day++;
          }
        }
        echo '</tr>';
        $weekday = 0;
      }
    ?>
  </tbody>
</table>

<form method="post">
  <select name="year">
    <?php
      for ($i = 1970; $i < 2100; $i++) {
        echo '<option value="' . $i . '">' . $i . '年</option>';
      }
    ?>
  </select>
  <select name="month">
    <?php
      for ($i = 1; $i <= 12; $i++) {
        echo '<option value="' . str_pad($i, 2, 0, STR_PAD_LEFT) . '">' . $i . '月</option>';
      }
    ?>
  </select>
  <input type="submit" value="查询">
</form>

table td:nth-child(3):before {
  content: '元旦';
  font-size: 14px;
  color: #f00;
}