how to run native Windows app, like calc, notepad, using php?

I am going to assume that this question has nothing to do with DigitalOcean services since we do not offer a Windows OS option at this time. That being out of the way there are a couple ways to execute a command on the host system from within php though I am not sure how GUI applications will handle this on Windows as my experience with PHP is almost exclusively on Linux/FreeBSD hosts.

backticks:

`C:/path/to/app.exe`;

system:

system('C:/path/to/app.exe');

exec:

exec('C:/path/to/app.exe');

Ok. thanks.