<?php
class fancyCache
{
private static $_instance = NULL;

protected $_options =array();

/**
* 初始化構造函數
* $cacheDir : 緩存文件目錄
* $expire : 緩存文件有效期,單位為秒
* $file_ext ： 緩存文件后綴
*/
public static function init($cacheDir='./cache',$expire=1800,$file_ext='.htm')
{
$instance = self::getInstance();

//判斷緩存目錄是否有效
if($instance->isValidCacheDir($cacheDir))
{
$instance->_options['cache_dir']=rtrim($cacheDir,'/') . '/';
$instance->_options['expire']=$expire;
$instance->_options['file_ext']=$file_ext;
$instance->_options['cache_file_url']=$instance->getCacheFileUrl();

if($_SERVER['REQUEST_METHOD']=='GET')
{
//緩存未過期則讀取緩存文件
if($instance->isExpired()) {
$instance->readCache();
exit;
}
else
{
//自動緩存
ob_start(array($instance,"autoCache"));
}
}
else
{
//不是GET請求則刪除緩存
if(file_exists($instance->_options['cache_file_url']))unlink($instance->_options['cache_file_url']);
}
}
}
/**
* 獲取當前對象
*/
public static function getInstance()
{
if(self::$_instance==NULL)
{
self::$_instance=new self();
}
return self::$_instance;
}
/**
* 讀取緩存
*/
protected function readCache()
{
$instance =self::getInstance();
$fp =fopen($instance->_options['cache_file_url'],'rb');

fpassthru($fp);
fclose($fp);
}

/**
* 自動寫入緩存
*/
public function autoCache($contents)
{
$instance = self::getInstance();

if($fp=fopen($instance->_options['cache_file_url'],'wb'))
{
if (flock($fp, LOCK_EX))
{
ftruncate($fp,0);
fwrite($fp, $contents);
fclose($fp);

chmod($instance->_options['cache_file_url'],0777);
}
}
self::DelOldCache();

return $contents;
}
/**
* 刪除所有過期緩存
*/
protected function DelOldCache()
{
$instance = self::getInstance();

chdir($instance->_options['cache_dir']);

foreach (glob("*/*".$instance->_options['file_ext']) as $file)
{
if(time()-filemtime($file)>$instance->_options['expire'])unlink($file);
}
}

/**
* 驗證緩存是否有效
* return true 已過期
*/
protected function isExpired()
{
$instance = self::getInstance();

if(!file_exists($instance->_options['cache_file_url']))return false;

if(time()-filemtime($instance->_options['cache_file_url'])>$instance->_options['expire'])return false;

return true;
}

/**
* 驗證緩存目錄是否存在，不存在則創建
* return true 存在或創建成功
*/
protected function isValidCacheDir($cacheDir)
{
$instance = self::getInstance();
$cacheDir=rtrim($cacheDir,'/') . '/';

if(!file_exists($cacheDir)){
try
{
mkdir($cacheDir,0777);
chmod($cacheDir,0777);
}
catch(Exception $e)
{
echo 'Failed to create cache dir!';
return false;
}
}
//創建緩存文件子目錄
$cacheFileDir=$cacheDir.substr(md5($instance->getPageUrl()),0,1);

if(!file_exists($cacheFileDir))
{
try
{
mkdir($cacheFileDir,0777);
chmod($cacheFileDir,0777);
}
catch(Exception $e)
{
echo 'Failed to create cache dir!';
return false;
}
}

return true;
}

/**
* 取得緩存文件路徑
*/
protected function getCacheFileUrl()
{
$instance =self::getInstance();
$pageUrl =md5($instance->getPageUrl());

return $instance->_options['cache_dir'].substr($pageUrl,0,1).'/'.$pageUrl.$instance->_options['file_ext'];
}

/**
* 取得當前訪問頁面完整url
*/
protected function getPageUrl() {
$url = '';
if (isset($_SERVER['REQUEST_URI'])) {
$url = $_SERVER['REQUEST_URI'];
}
else {
$url = $_SERVER['PHP_SELF'];
$url .= empty($_SERVER['QUERY_STRING'])?'':'?'.$_SERVER['QUERY_STRING'];
}
return $url;
}
}
?>