WP-admin not accessible

Hi,

I’ve just moved a website from one domain to the other. WP-admin doesn’t work. Instead it gives me a window to download the php file to my computer.

The website is working like it should.

I tried manually updating WP to 3.5.1 but it seems like it didn’t work as it still shows 2.7.1. Before transfering the site, the wp-admin page showed a white page with php errors on different lines in wp-admin.

Any help to access the backend is greatly appreciated!!