用php开发网站，一般都要尽量避免数据库查询以减少服务器压力，可随着网站内容增多，访问量上升，服务器还是不堪重负。直接生成静态页面是一个办法，可页面越来越多的时候，管理起来非常困难。更好的解决办法就是用缓存，首次访问的时候先检查是否已经缓存和缓存是否过期，有则直接返回，没有或者过期才去数据库查询，处理后返回html。这种机制真是个好主意，可代码应该怎么写呢？ 别担心，github上面已经有人写好了，超级好用，快试试吧，源码如下：

class Cache {

    // Pages you do not want to Cache:

    var $doNotCache = array("admin");  // 不缓存的页面

    // General Config Vars

    var $cacheDir = "cache";

    var $cacheTime = 36000; // 缓存文件有效期

    var $caching = false;

    var $cacheFile;

    var $cacheFileName;

    var $cacheLogFile;

    var $cacheLog;

    function __construct(){

        $this->cacheFile = base64_encode($_SERVER['REQUEST_URI']);

        $this->cacheFileName = $this->cacheDir.'/'.$this->cacheFile.'.txt';

        $this->cacheLogFile = $this->cacheDir."/log.txt";

        if(!is_dir($this->cacheDir)) mkdir($this->cacheDir, 0755);

        if(file_exists($this->cacheLogFile))

            $this->cacheLog = unserialize(file_get_contents($this->cacheLogFile));

        else

            $this->cacheLog = array();

    }

    function start(){

        $location = array_slice(explode('/',$_SERVER['REQUEST_URI']), 0);

        if(!in_array($location[2],$this->doNotCache)){

            if(file_exists($this->cacheFileName) && (time() - filemtime($this->cacheFileName)) < $this->cacheTime && $this->cacheLog[$this->cacheFile] == 1){

                $this->caching = false;

                echo file_get_contents($this->cacheFileName);

                exit();

            }else{

                $this->caching = true;

                ob_start();

            }

        }

    }

    function end(){

        if($this->caching){

            file_put_contents($this->cacheFileName,ob_get_contents());

            ob_end_flush();

            $this->cacheLog[$this->cacheFile] = 1;

            if(file_put_contents($this->cacheLogFile,serialize($this->cacheLog)))

                return true;

        }

    }

    function purge($location){

        $location = base64_encode($location);

        $this->cacheLog[$location] = 0;

        if(file_put_contents($this->cacheLogFile,serialize($this->cacheLog)))

            return true;

        else

            return false;

    }

    function purge_all(){

        if(file_exists($this->cacheLogFile)){

            foreach($this->cacheLog as $key=>$value) $this->cacheLog[$key] = 0;

            if(file_put_contents($this->cacheLogFile,serialize($this->cacheLog)))

                return true;

            else

                return false;

        }

    }

}

网站首页入口处：

include_once("class.cache.php");

$cache = new Cache;

$cache->start();

最后：

$cache->end();

来源：http://chainjoy.com/blog/php/75.html