expires header on php generated image

[henryrhenryr]

I am trying to make my php-generated images cache. Here is a summary of the script with the headers. It doesn't seem to cache though. Do I need to do something special to make sure it caches?

[code=php]
//summarised

//resize...
$file= $_GET['file'];
$o= imagecreatefrom gif($file);
$i= imagecreatetrue color($w,$h);
imagecopyresamp led($i,$o,0,0,0 ,0,$w,$h,$wo,$h o);

//output
header('Content-type: image/gif');
header('Expires : '.date(DATE_RFC 1123,time()+259 2000));
imagegif($i);
imagedestroy($i );

[/code]

Here are the response headers (using firebug). The server clearly gets the expires header. But I still have the overhead showing in firebug.

Date Tue, 29 Jul 2008 13:06:36 GMT
Server Apache/2.0.55 (Ubuntu) PHP/5.1.2
X-Powered-By PHP/5.1.2
Expires Thu, 28 Aug 2008 14:06:36 BST
Content-Length 2182
Keep-Alive timeout=15, max=95
Connection Keep-Alive
Content-Type image/gif

[pbmods]

Heya, Henry.

I hate to just drop an article on you, but I have to run out the door in a sec. In the meantime, perhaps this article will have some information that you might find useful (http://www.mnot.net/cache_docs/).

And I am now subscribed to this thread (:

[henryrhenryr]

I hate to just drop an article on you,

That's fine! I'd seen this one but it seems like it was one of those occasions where I just didn't type the right thing into google yesterday!

I just found this:

http://php.dtbaker.com.au/post/caching_images_from_php_imagejpeg

The solution is to use the last-modified header based on the filemtime() for the input file. The article has a solution if you have no input file too. The browser now caches the images. I hope it will refresh when they are updated!

[code=php]
//summarised
//two additions - check last-modified header and exit if same as
//filemtime(), also set last-modified header

//resize...
$file= $_GET['file'];

if (isset($_SERVER['HTTP_IF_MODIFI ED_SINCE']) && strtotime($_SER VER['HTTP_IF_MODIFI ED_SINCE'])==filemtime($f ile)) {
header('Last-modified: '.date(DATERFC_ 1123,filemtime( $file)),true,30 4);
exit;
}

$o= imagecreatefrom gif($file);
$i= imagecreatetrue color($w,$h);
imagecopyresamp led($i,$o,0,0,0 ,0,$w,$h,$wo,$h o);

//output
header('Content-type: image/gif');
header('Expires : '.date(DATE_RFC 1123,time()+259 2000));
header('Last-modified: '.date(DATE_RFC 1123,filemtime( $file);
imagegif($i);
imagedestroy($i );

[/code]