Advise on SEO-friendly URL structures

My site is written in php and has urls like this:

http://mysite.com/index.php?m=apple&f=show&t=开发者_JAVA百科hello-world

I want to change it to SEO friendly url.but i don't know which one is better:

http://mysite.com/apple/hello-world

or

http://mysite.com/apple/hello-world.html

would you help me?

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I would not include the .html. It doesn't help your users at all. In general, if it is good for users it is good for SEO.

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Try to avoid extensions where possible, as they may change over time, and URIs should remain static. Think about old sites that use the .cgi extension, and then migrated to another system, such as PHP. Although HTML is likely to be around for a long time, it too may change.

See Cool URIs don't change for a good introduction.