Impact on Google when removing page extenstions

Hi guys,

I am currently looking at using .htaccess to remove the .php extensions from the URL. I am able to do this fine but wondered how this would impact on the Google SERP's?

Will it see /page1.php differently from /page1. Will it see it as a completely separate page?

And also, I will have external links still pointing to /page1.php. Will this matter?

Any advice/help/tips would be appreciated.

Thanks all,

BIOSTALL