详细讲解PHP中缓存技术的应用_PHP教程

<?php
classcache{
/*
ClassName:cache
Description:controltocachedata,$cache_out_timeisaarraytosavecachedatetimeout.
Version:1.0
Author:老农cjjer
Lastmodify:2006-2-26
AuthorURL:http://www.cjjer.com
*/
private$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.');
returnfalse;
}
}
$this->cache_dir=$cache_dirname;
}
function__destruct(){
echo'Cacheclassbye.';
}
functionget_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;
}
functionwarn($errorstring){
echo"<b><fontcolor='red'>发生错误:<pre>".$errorstring."</pre></font></b>";
}
functioncache_page($pageurl,$pagedata){
if(!$fso=fopen($pageurl,'w')){
$this->warns('无法打开缓存文件.');//trigger_error
returnfalse;
}
if(!flock($fso,LOCK_EX)){//LOCK_NB,排它型锁定
$this->warns('无法锁定缓存文件.');//trigger_error
returnfalse;
}
if(!fwrite($fso,$pagedata)){//写入字节流,serialize写入其他格式
$this->warns('无法写入缓存文件.');//trigger_error
returnfalse;
}
flock($fso,LOCK_UN);//释放锁定
fclose($fso);
returntrue;
}
functiondisplay_cache($cacheFile){
if(!file_exists($cacheFile)){
$this->warn('无法读取缓存文件.');//trigger_error
returnfalse;
}
echo'读取缓存文件:'.$cacheFile;
//returnunserialize(file_get_contents($cacheFile));
$fso=fopen($cacheFile,'r');
$data=fread($fso,filesize($cacheFile));
fclose($fso);
return$data;
}
functionreadData($cacheFile='default_cache.txt'){
$cacheFile=$this->cache_dir."/".$cacheFile;
if(file_exists($cacheFile)&&filemtime($cacheFile)>(time()-$this->expireTime)){
$data=$this->display_cache($cacheFile);
}else{
$data="fromherewocangetitfrommysqldatabase,updatetimeis<b>".date('ldSofFYh:i:sA')."</b>,过期时间是:".date('ldSofFYh:i:sA',time() $this->expireTime)."----------";
$this->cache_page($cacheFile,$data);
}
return$data;
}

}
?>