ASP to PHP

I have several questions about converting a site from ASP to PHP and
the effect.

1.    Will there be any adverse effect on SERPs or Page Rank by
converting?

2.    URLs will be changed to  - mysite.com/a/b/c.asp to
mysite.com/a/b/c.php.  Are these two URLs viewed by search engines as
the same URL?

3.    Are there any other issues that I should be aware of, in regards to
converting an existing site to PHP, as it relates to the SERPs and
their current positions?

I would appreciate any input.

Thanks,
Craig