install.php opens as code in browser

did you try right clicking it and then opening with notepad, or your favorite text editor? just choose the program.

courtney brazley

:end

Download a fresh copy of WP and replace the old files

You can not click on install.php expect it open wordpress.

WordPress is a server program needs to install on a server.
If you have host account then you upload and install.

https://codex.www.ads-software.com/Installing_WordPress#Famous_5-Minute_Install

or you if want to install on your computer then you will need install Wamp or Xampp for windows and Mamp for Mac and then install wordpress.