PHP files downloading instead of running?

Are you trying to use URL rewrite (www.domain.com/index.php?admin --> www.domain.com/admin)?

In .htaccess file you are telling .php files to be run through PHP parser - I wonder if it doesn't recognise that you are redirecting everything to index.php, and uses URL (www.domain.com/admin) instead, which now doesn't have .php file extension.

I am trying with tp://www.domain.com/admin. please help me out.