I found a quirk in WampServer that cost me several hours to figure out. I thought I'd share in case anyone else was having the same difficulty:
I updated my MS Visual C++ package, installed the correct version of Wampserver, put my files in the "www" folder, etc. The server was green and running, but my PHP code would not execute.
One thing was my mistake. I thought I could use the browser to access the file, but I learned that you have to go through LocalHost to open the file.
Another was a weird quirk. Watching videos on the internet, I saw others simply go to LocalHost and click on their project in "My Projects" and their webpages came up. For me, I kept getting "File not found". Scrutinizing the address bars in the videos, I realized that when people in the video clicked, the address would read "localhost/test/test.php" (adding the name of the folder and file to the address) but for me, the address would just read "test.php" (without the localhost, etc. at the beginning) Adding it in manually, the webpage finally came up in PHP.
Hopefully this helps someone else. I don't know if I'm doing something wrong, but at least I can find my files!
(Windows 10 / x64)