用php開發(fā)網(wǎng)站，一般都要盡量避免數(shù)據(jù)庫查詢以減少服務(wù)器壓力，可隨著網(wǎng)站內(nèi)容增多，訪問量上升，服務(wù)器還是不堪重負(fù)。直接生成靜態(tài)頁面是一個(gè)辦法，可頁面越來越多的時(shí)候，管理起來非常困難。更好的解決辦法就是用緩存，首次訪問的時(shí)候先檢查是否已經(jīng)緩存和緩存是否過期，有則直接返回，沒有或者過期才去數(shù)據(jù)庫查詢，處理后返回html。這種機(jī)制真是個(gè)好主意，可代碼應(yīng)該怎么寫呢？ 別擔(dān)心，github上面已經(jīng)有人寫好了，超級(jí)好用，快試試吧，源碼如下：

class Cache {

    // Pages you do not want to Cache:

    var $doNotCache = array("admin");  // 不緩存的頁面

    // General Config Vars

    var $cacheDir = "cache";

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

    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;

        }

    }

}

網(wǎng)站首頁入口處：

include_once("class.cache.php");

$cache = new Cache;

$cache->start();

最后：

$cache->end();

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