You cannot do it like that. The path you are using is a url on a web-server and according to the manual:
This is not strictly speaking the same thing as including the file and
having it inherit the parent file's variable scope; the script is
actually being run on the remote server and the result is then being
included into the local script.
So your php file is being parsed / executed on the Raspberry and all you get back are the results so there are not functions to execute.
Unless Stb.php
outputs php code of course, but that seems very unlikely from what I understand from the question...
If this is on a local network, you could make it work if you can mount the file-system of the Raspberry on your pc so that you can use a file path like for example:
include '/mnt/Raspberry/Stb.php';
(assuming something like linux or OSX, on Windows it would be a bit different)