Question

I have a php script acting as a random image generator. The script queries the database for the user’s images, and returns the path to one, at random. Here is the portion of the code responsible for returning the image, once the path has been chosen.

header('Content-Transfer-Encoding: binary');
header('Content-Type: image/jpeg');
header('Content-Length: ' . filesize($path));
echo file_get_contents($path);

I am calling it from the client like so

image.src = "/database/getRandomImage.php";

Every time I refresh the page I get a new image at random. However, if I call getRandomImage.php multiple times for side by side images, they will all be the same image. If I add a random property to the call like so

image.src = "/database/getRandomImage.php?path=" + Math.random() * 100;

The pictures become random. I take this to mean that the browser is caching them based on the random property I passed. The problem is this property has nothing to do with the actual image. Two different images might get cached as the same image, and the same image might not be retrieved from the cache. Is there any way for getRandomImage.php to inform the browser about the picture it is sending back?

Answer 1

Why not have getRandomImage be a PHP function, which returns a path to the image. You can render the page out with the random image paths already filled in.

<img src="<? echo getRandomImage() ?>">

Then you can actually serve your images with real cache headers, and your bandwidth wont be getting hammered so hard.

Do this on the server side while the page is rendering, not after. Doing it after is more work and, as you are finding out, is more complicated too.