PHP缓存问题

我有一个类缓存一些图像PHP缓存问题

<?php 
class Vp_CacheImage 
{ 
    public function cache($cacheTime, $place) // $place = id of image (between 1 and 100) 
    { 
     $send_body = true; 
     $etag = '"' . md5(date('d.m.Y', time()) . $place) . '"'; 
     header("ETag: " . $etag); 
     header("Last-modified: " . gmdate("D, d M Y H:i:s", $cacheTime) . " GMT"); 

     $inm = explode(',', getenv("HTTP_IF_NONE_MATCH")); 
     foreach ($inm as $i) 
     { 
      if (trim($i) == $etag || trim($i) == $cacheTime) 
      { 
       header ("HTTP/1.0 304 Not Modified"); 
       $send_body = false; 
      } 
     } 

     if(getenv("HTTP_IF_MODIFIED_SINCE") == gmdate("D, d M Y H:i:s", $cacheTime). " GMT") 
     { 
      header ("HTTP/1.0 304 Not Modified"); 
      $send_body = false; 
     } 

     header("Expires: " . gmdate("D, d M Y H:i:s", time() + Config::$config['cache']['images']['topvideo']) . " GMT"); 
     header("Cache-Control: max-age=" . Config::$config['cache']['images']['topvideo'] . ", must-revalidate"); 
     if ($send_body) return true; else return false; 
    } 
}

它的工作原理。但是我必须有时重新加载一张图片，而不是从缓存中取出。怎么做？

来源

2010-11-23 Isis