Best way to cache resized images using PHP and MySQL

Question

What would be the best practice way to handle the caching of images using PHP.

The filename is currently stored in a MySQL database which is renamed to a GUID on upl

Answer 1

I've managed to do this simply using a redirect header in PHP:

if (!file_exists($filename)) {  

    // *** Insert code that generates image ***

    // Content type
    header('Content-type: image/jpeg'); 

    // Output
    readfile($filename);    

} else {
    // Redirect
    $host  = $_SERVER['HTTP_HOST'];
    $uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
    $extra = $filename;
    header("Location: http://$host$uri/$extra");
}

Answer 2

phpThumb is a framework that generates resized images/thumbnails on the fly. It also implements caching and it's very easy to implement.

The code to resize an image is:

<img src="/phpThumb.php?src=/path/to/image.jpg&w=200&amp;h=200" alt="thumbnail"/>

will give you a thumbnail of 200 x 200;

It also supports watermarking.

Check it out at: http://phpthumb.sourceforge.net/

Answer 3

Your approach seems quite reasonable - I would add that some mechanism should be put into place to check that the date the cached version was generated was after the last modified timestamp of the original (source) image file and if not regenerate the cached/resized version. This will ensure that if an image is changed by the designers the cache will be updated appropriately.