php缓存类

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<?php
final class FileCache
{
    /**
     * * * 缓存目录 *
     * 
     * @var string 
     */
    private static $msCachePath = null;
    /**
     * * * 默认缓存失效时间(1小时) *
     * 
     * @var int 
     */
    const miEXPIRE = 3600;
    /**
     * * * 构造<br /> * self::$msCachePath 缓存目录为共享目录 *
     * 
     * @param string $sCachePath 
     */
    function __construct($sCachePath = './tmp/')
    {
        if (is_null(self :: $msCachePath))
            self :: $msCachePath = $sCachePath;
    } 
    /**
     * * * 读取缓存<br /> * 返回: 缓存内容,字符串或数组；缓存为空或过期返回null *
     * 
     * @param string $sKey 缓存键值(无需做md5()) *
     * @return string | null *
     * @access public 
     */
    public function get($sKey)
    {
        if (empty($sKey))
            return false;
        $sFile = self :: getFileName($sKey);
        if (!file_exists($sFile))
            return null;
        else
        {
            $handle = fopen($sFile, 'rb');
 
            if (intval(fgets($handle)) > time())
            { 
                // 检查时间戳 {  //未失效期，取出数据
                $sData = fread($handle, filesize($sFile));
                fclose($handle);
                return unserialize($sData);
            } 
            else
            { 
                // 已经失效期
                fclose($handle);
                return null;
            } 
        } 
    } 
    /**
     * 写入缓存 * *
     * 
     * @param string $sKey 缓存键值 *
     * @param mixed $mVal 需要保存的对象 *
     * @param int $iExpire 失效时间 *
     * @return bool 
     * @access public 
     */
    public function set($sKey, $mVal, $iExpire = null)
    {
        if (empty($sKey))
            return false;
        $sFile = self :: getFileName($sKey);
        if (!file_exists(dirname($sFile)))
            if (!self :: is_mkdir(dirname($sFile)))
                return false;
            $aBuf = array();
            $aBuf[] = time() + ((empty($iExpire)) ? self :: miEXPIRE : intval($iExpire));
            $aBuf[] = serialize($mVal);
            /**
             * 写入文件操作
             */
            $handle = fopen($sFile, 'wb');
            fwrite($handle, implode("\\n", $aBuf));
            fclose($handle);
            return true;
        } 
        /**
         * * * 删除指定的缓存键值 *
         * 
         * @param string $sKey 缓存键值
         * @return bool 
         */
 
        public function del($sKey)
        {
            if (empty($sKey))
                return false;
            else
            {
                @unlink (self :: getFileName($sKey));
                return true;
            } 
        } 
        /**
         * * * 获取缓存文件全路径<br /> * 返回: 缓存文件全路径<br /> * $sKey的值会被转换成md5(),并分解为3级目录进行访问 *
         * 
         * @param string $sKey 缓存键 *
         * @return string 
         * @access protected 
         */
 
        private static function getFileName($sKey)
        {
            if (empty($sKey)) return false;
            $key_md5 = md5($sKey);
            /**
             * $aFileName = array();
             * $aFileName[] = rtrim(self :: $msCachePath, '/');
             * $aFileName[] = $key_md5{0} . $key_md5{1};
             * $aFileName[] = $key_md5{2} . $key_md5{3};
             * $aFileName[] = $key_md5{4} . $key_md5{5};
             * $aFileName[] = $key_md5;
             */
            return self :: $msCachePath . '/' . $key_md5; 
            // return implode('/', $aFileName);
        } 
        /**
         * * * 创建目录<br /> * *
         * 
         * @param string $sDir 
         * @return bool 
         */
        private static function is_mkdir($sDir = '')
        {
            if (empty($sDir))
                return false;
            /**
             * 如果无法创建缓存目录，让系统直接抛出错误提示
             */
            echo $sDir;
            if (!mkdir($sDir, 0666))
                return false;
            else
                return true;
        } 
    }
//该片段来自于http://yuncode.net
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