Dyanmic Images Reload

I have a php script that dynamically creates images, reusing image files on
the server to save space and clutter.

The problem is described in the steps below:

1. User clicks on a button.
2. Same page loads, but the php script creates a new image in an old file.
3. It displays the image file, but the old image shows, even though the file
contains the new image.

My options are:

1. Use javascript to force a reload when the user clicks the button (not
desirable, because the user is forced to confirm the reload by the browser).
2. Put a cheesy blurb on the page telling the user to reload or refresh
(along with ideotic explanations of how to do it).
3. Some really great way someone here is going to describe to me (my
preference).