The danger is putting server-side code in a file that the server might not recognize as executable. You can have the same problem using ASP or any other server-side scripting technology. If the server isn't configured to run .inc files through the server-side script interpreter, it will just perform the default action (send the file contents unmodified) if another system requests it. To fix this, you can reconfigure the server to treat .inc files as PHP code, or, since the file extension isn't really important anyway, you can just give all your files a .php extension. That way, if you later move the code to another server, you don't have to worry about it, because you know a .php extension will always work.