class cache{
/*
class name: cache
description: control to cache data,$cache_out_time is a array to save cache date time out.
version: 1.0
author: 老农 cjjer
last modify:2006-2-26
author url: http://www.phprm.com
private $cache_dir;
private $expiretime=180;//缓存的时间是 60 秒
function __construct($cache_dirname){
    if(!@is_dir($cache_dirname)){
        if(!@mkdir($cache_dirname,0777)){
        $this->warn('缓存文件不存在而且不能创建,需要手动创建.');
        return false;
        }
    }
$this->cache_dir    =    $cache_dirname;
}
function __destruct(){
    echo 'cache class bye.';
}

function get_url() {
        if (!isset($_server['request_uri'])) {
                $url = $_server['request_uri'];
        }else{
                $url = $_server['script_name'];
                $url .= (!empty($_server['query_string'])) ? '?' . $_server['query_string'] : '';
        }

        return $url;
}

function warn($errorstring){
echo "<b><font color='red'>发生错误:<pre>".$errorstring."</pre></font></b>";
}

function cache_page($pageurl,$pagedata){
    if(!$fso=fopen($pageurl,'w')){
        $this->warns('无法打开缓存文件.');//trigger_error
        return false;
    }
    if(!flock($fso,lock_ex)){//lock_nb,排它型锁定
        $this->warns('无法锁定缓存文件.');//trigger_error
        return false;
    }
    if(!fwrite($fso,$pagedata)){//写入字节流,serialize写入其他格式
        $this->warns('无法写入缓存文件.');//trigger_error
        return false;
    }
    flock($fso,lock_un);//释放锁定
    fclose($fso);
    return true;
}