I think this happened shortly after a clean up of the computer when a 'never used' file folder called 'apache' was deleted!
Apache is a web server, commonly used to display PHP websites. When it is working correctly, you shouldn't really be aware that it is there. (The same, by the way, can be said about most software that runs on your PC.)
You can download and install Apache fairly simply, but setting it up to work the way your old installation worked could be tricky. For one, I have no idea
how it was set up, and seeing as you deleted the old files I'm guessing you don't either.
To set up Apache to work with PHP, you can simply download the
Apache server and
PHP separately and install them one after the other. There should be Windows installers available for both, and most Linux distros have them available in whichever package distribution system they use.
You can also use developer packages like
XAMPP, which installs everything PHP websites may need at the same time. May be a bit much but it could be easier to set up.
Note that neither of these methods is likely to work as a drop-in replacement for the files you deleted. You will most likely have to configure them to get them working like your old installation. - If you can't figure out how to set it up as it was, there is little hope that I will be able to. Your best bet would be to find whoever set it up in the first place and ask them.