简单的PHP日历算法

/** 
  * 日历 
  * 
  * Copyright(c) 2007 by 陈毅鑫(深空). All rights reserved 
  * To contact the author write to {@link mailto:shenkong@php.net} 
  * @author 陈毅鑫(深空) 
  */
 if (function_exists('date_default_timezone_set')) { 
     date_default_timezone_set('Asia/Chongqing'); 
 } 
 $date = isset($_GET['date']) ? $_GET['date'] : date('Y-m-d'); 
 $date = getdate(strtotime($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'])); 
 $pre = date('Y-m-d', $start[0] - 1); 
 $next = date('Y-m-d', $end[0] + 86400); 
 $html = '