Detailed explanation on the definition and use of redis cache class in PHP

<?php
class redisCache {
  /**
  * $host : redis服务器ip
  * $port : redis服务器端口
  * $lifetime : 缓存文件有效期,单位为秒
  * $cacheid : 缓存文件路径,包含文件名
  */
  private $host;
  private $port;
  private $lifetime;
  private $cacheid;
  private $data;
  public $redis;
  /**
  * 析构函数,检查缓存目录是否有效,默认赋值
  */
  function __construct($lifetime=1800) {
    //配置
    $this->host = "127.0.0.1";
    $this->port = "6379";
    $redis = new Redis();
    $redis->pconnect($this->host,$this->port);
    $this->redis=$redis;
    $this->cacheid = $this->getcacheid();
    $this->lifetime = $lifetime;
    $this->data=$redis->hMGet($this->cacheid, array(&#39;content&#39;,&#39;creattime&#39;));
    //print_r($this->redis);
    //print_r($this->data);
  }
  /**
  * 检查缓存是否有效
  */
  private function isvalid(){
    $data=$this->data;
    if (!$data[&#39;content&#39;]) return false;
    if (time() - $data[&#39;creattime&#39;] > $this->lifetime) return false;
    return true;
  }
  /**
  * 写入缓存
  * $mode == 0 , 以浏览器缓存的方式取得页面内容
  */
  public function write($mode=0,$content=&#39;&#39;) {
    switch ($mode) {
      case 0:
        $content = ob_get_contents();
        break;
      default:
        break;
    }
    ob_end_flush();
    try {
      $this->redis->hMset($this->cacheid, array(&#39;content&#39;=>$content,&#39;creattime&#39;=>time()));
      $this->redis->expireAt($this->cacheid, time() + $this->lifetime);
    }
    catch (Exception $e) {
      $this->error(&#39;写入缓存失败!&#39;);
    }
  }
  /**
  * 加载缓存
  * exit() 载入缓存后终止原页面程序的执行,缓存无效则运行原页面程序生成缓存
  * ob_start() 开启浏览器缓存用于在页面结尾处取得页面内容
  */
  public function load() {
    if ($this->isvalid()) {
      echo $this->data[&#39;content&#39;];
      exit();
    }
    else {
      ob_start();
    }
  }
  /**
  * 清除缓存
  */
  public function clean() {
    try {
      $this->redis->hDel($this->cacheid, array(&#39;content&#39;,&#39;creattime&#39;));
    }
    catch (Exception $e) {
      $this->error(&#39;清除缓存失败!&#39;);
    }
  }
  /**
  * 取得缓存文件路径
  */
  private function getcacheid() {
    return $this->dir.md5($this->geturl()).$this->ext;
  }
  /**
  * 取得当前页面完整url
  */
  private function geturl() {
    $url = &#39;&#39;;
    if (isset($_SERVER[&#39;REQUEST_URI&#39;])) {
      $url = $_SERVER[&#39;REQUEST_URI&#39;];
    }
    else {
      $url = $_SERVER[&#39;Php_SELF&#39;];
      $url .= empty($_SERVER[&#39;QUERY_STRING&#39;])?&#39;&#39;:&#39;?&#39;.$_SERVER[&#39;QUERY_STRING&#39;];
    }
    return $url;
  }
  /**
  * 输出错误信息
  */
  private function error($str) {
    echo &#39;<p style="color:red;">&#39;.$str.&#39;</p>&#39;;
  }
}
//用法：
// require_once(&#39;redisCache.php&#39;);
// $cache = new redisCache(10); //设置缓存生存期
// if ($_GET[&#39;clearCache&#39;]) $cache->clean();
// else $cache->load(); //装载缓存,缓存有效则不执行以下页面代码
// //页面代码开始
// //页面代码结束
// $cache->write(); //首次运行或缓存过期,生成缓存
?>