Here's an idea off the top of a pretty tired head: adjust your server configuration so that any file requests that don't match anything otherwise recognisable have PHP as a last resort. So, after dealing with files that end with .gif, .jpeg, .html and all the other MIME types you've got there, those that are left (including files without file extensions) are treated as PHP.
You'll probably want to do this on a per-directory basis to limit the insanity.