Different PR for index.php?

Question. How come these two URLS's have different PR's?

http://www.khmerauction.com/index.php PR 1
http://www.khmerauction.com/ PR 2

Thanks.

 

because they are two different pages, you should redirect the index.php to the root/

 

Yes i am agree Google treat as deferant page
Like http://domain.com
http://www.domain.com
http://www.domain.com/index.php or http://www.domain.com/index.html

These are same pages for you but for Google these are deferent pages use .httacess for prevent this.