php caching problem

Question

I have a class for caching some images

<?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;
    }
}

It works. But I have to make a picture reloaded sometimes, and not taken from cache. How to do it?

Wouter Dorgelo · Accepted Answer · 2010-11-23 19:48:30Z

2

Then you have to remove it from your cache first, or.. add temp. a random token, like: ?x=234 behind it and reload it.

You can also set expire to the moment right before you reload it, but that's tricky.

edited Nov 23, 2010 at 19:48

answered Nov 23, 2010 at 19:42

Wouter Dorgelo

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1 Comment

Wouter Dorgelo Over a year ago

You can also set expire to the moment right before you reload it, but that's tricky. might be not possible while you probably don't know when you need to reload it.

Spektr · Accepted Answer · 2010-11-23 19:43:24Z

0

Can you simply append a version to the image URL? Example: myimage.jpg?v=10

Doing so will cause the browser to request a fresh copy of the image rather than use the cached one.

answered Nov 23, 2010 at 19:43

Spektr

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simshaun · Accepted Answer · 2010-11-23 19:43:41Z

0

The easiest way of forcing the browser to fetch the image again is to append a query string to the end of the filename.

e.g. <img src="/assets/images/abc.png?v2">

answered Nov 23, 2010 at 19:43

simshaun

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