用php语言写出一个日历表

在PHP中创建一个简单的日历表，我们可以使用内建函数`date()`来生成每个月的日历。下面是一个基本的例子：

<?php
function createCalendar($year = date('Y'), $month = date('m')) {
    // 设置月份和年份
    if ($month < 1 || $month > 12) {
        die("Invalid month");
    }
    $daysInMonth = cal_days_in_month(CAL_GREGORIAN, $month, $year);

    // 获取当前月份的第一天是星期几
    $firstDayOfWeek = date('w', strtotime("{$year}-{$month}-01"));

    echo "<table border='1'>";
    echo "<tr><th></th>";
    for ($i = 0; $i <= 6; $i++) {
        echo "<th>".date('l', strtotime("{$year}-{$i + 1}"))."</th>";
    }
    echo "</tr>";

    // 输出每一天
    for ($day = 1; $day <= $daysInMonth; $day++) {
        $class = $day == date('j') ? 'today' : '';
        echo "<tr>";
        echo "<td class='$class'>$day</td>";
        for ($i = 0; $i < $firstDayOfWeek - 1 && $day != 1; $i++) {
            echo "<td>&nbsp;</td>";
        }
        while ($day != 1) {
            $day--;
            echo "<td>&nbsp;</td>";
        }
        for ($i = 0; $i < 7 - ($firstDayOfWeek - 1); $i++) {
            echo "<td>&nbsp;</td>";
        }
        echo "</tr>";
    }
    echo "</table>";
}

createCalendar();