Urgent: How do I disallow a php/html file to act as a folder?

["Daniel Anderson" <shadowedmyth@xxxxxxxxxxx>]

I recently noticed that for some reason, if I type the filename as a folder ("http://localhost/folder/";) it runs the nearest file called that.

I have several .php on a server, which can run without the extention. ("http://localhost/folder/file";), but if I typed ("http://localhost/folder/file/";) it'll still run that file. And to save time, I have made a header and footer for each of the pages I make, so it does not consume more time re-adding them everytime I create a new document.

Is there a way that I can disable this?

So that a file (php, html, jsp, etc.) can't be launched as a folder, but can still be launched without the file extension?

So:

http://localhost/folder/file works,

http://localhost/folder/file.php works

but:

http://localhost/folder/file/ doesn't unless there is a folder called "file".

I don't know if this is a PHP problem, or an Apache problem.

Thanks,

Dan