php 写一个日历的程序

php写一个calender的例子：

<?php
if (function_exists('date_default_timezone_set')) {
     date_default_timezone_set('Asia/Chongqing');
}
$date = isset($_GET['date'])?$_GET['date']:date('Y-m-d');
//var_dump($date);
$date = getdate(strtotime($date));
//print_r($date);

$end = getdate(mktime(0, 0, 0, $date['mon'] + 1, 1, $date['year']) - 1);
$start = getdate(mktime(0, 0, 0, $date['mon'], 1, $date['year']));

//var_dump($start);
$pre = date('Y-m-d', $start[0] - 1);
$next = date('Y-m-d', $end[0] + 86400);
//var_dump($pre);
//var_dump($next);

$html = '<table width="200" border="1" cellspacing="0" bordercolor="#999999"
    align="center" style="line-height:150%; font-family:Verdana,宋体; font-size: 12px;">';
$html .= '<tr>';
$html .= '<td><a href="' . $PHP_SELF . '?date=' . $pre . '">-</a></td>';
$html .= '<td colspan="5">' . $date['year'] . ';' . $date['month'] . '</td>';
$html .= '<td><a href="' . $PHP_SELF . '?date=' . $next . '">+</a></td>';
$html .= '</tr>';
$week_arr = array(Su,Mo,Tu,We,Th,Fr,Sa);
$html .= '<tr>';
foreach($week_arr as $v){
    $html .= '<td>'.$v.'</td>';
}
$html .= '</tr>';


$arr_tpl = array(0 => '', 1 => '', 2 => '', 3 => '', 4 => '', 5 => '', 6 => '');
$date_arr = array();
$j = 0;
for ($i = 0; $i < $end['mday']; $i++) {
    if (!isset($date_arr[$j])) {
        $date_arr[$j] = $arr_tpl;
    }
    $date_arr[$j][($i+$start['wday'])%7] = $i+1;
    if ($date_arr[$j][6]) {
        $j++;
    }
}

//var_dump($date_arr);
foreach ($date_arr as $value) {

    $html .= '<tr>';
    foreach ($value as $v) {
        if ($v) {
            if ($v == $date['mday']) {
                $html .= '<td><b>' . $v . '</b></td>';
            } else {
                $html .= '<td>' . $v . '</td>';
            }
        } else {
            $html .= '<td> </td>';
        }
    }
    $html .= '</tr>';
}
$html .= '</table>';
echo $html;
?>