Mod Rewrite Clean URL's

How can I transform:

• http://example.com开发者_开发问答/about.php
• http://example.com/hello/deep.php
• http://example.com/hello/world/deeper.php

Dynamically, into URLs like:

• http://example.com/about/
• http://example.com/hello/deep/
• http://example.com/hello/world/deeper/

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see http://gist.github.com/22877