Php upload - Webdav shared files

[danielread89]

I have a website which uploads files onto my website. I want users to be able to open the file from my website in whatever program they have on their computer. Example they open up a .txt file from my website it opens up on their computer in notepad. When they save the file I want it to save back to my website. I've been searching around for hours and I've been coming up with "webdav" but cannot figure out how to utilize this. I use Xampp to connect my websites. I see a webdav folder but when I try to upload something through PHP to that folder it says it's not allowed. Any information would be helpful and please be thorough as this is all new to me.