All my php pages are showing up as downloads

I just uploaded a new version of my code to my site, and now every php page is prompting me to download it instead of displaying it. How can I see what’s wrong here?

they show up as ‘application/x-httpd-php’ or ‘PHP file’

There may be something in .htaccess that’s changed the handler for .php files. So check your .htaccess file in your site’s root directory and lower than that if it’s not at root.