Sorry, but this irks me, please note that ALL uses of (.*) shown at http://httpd.apache.org/docs/2.2/rewrite/intro.html
(assuming this is the reference you are referring to) is for PATHS and FILENAMES, definitely never used with VARIABLES.
Granted, we are talking file names here so I will concede you can use it, however, I still never recommend it. As you are allowing more than what may be intended. It may be intended that you only consider the root directory, using (.*) permits ALL directories, that could very well be a security issue if you have admin pages, or files in folders you did not want to be a part of this rewriterule.
Back to the topic at hand, Jeff is correct you will end up in an infinite loop if you try to redirect *.php to its non-extension form, and you have a rule that internally redirects the non-extension form to .php. You will want to program the links to all of your pages to not use the extension so people browsing will never see the extension.