php缓存问题,php缓存问题

我有一个缓存一些图像的类

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;

}

}有用。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？