Browsing to my WP domain downloads a file

Just installed a fresh WP onto my domain using the same process I have several times before with success. When I browse to my domain or try to login to the admin panel a php file is downloaded rather than the page loading. See file contents below:
Please advise.

[Large code excerpt removed by moderator per forum rules. Please use the pastebin for all large code excerpts. It works better anyway.]