To view the session - file we need to know the path ( on localhost this is set normally c:/tmp & also on the Server ) The web server will not allow you to enter this directory , but you will be allowed to extract the file content as shown in red on top of this page.
$ID = c44631365ea2ce5c976d21290c21206c
( The session that the Server starts is the same as when using Funcions , if the browser session is the same , but data do not mix each other (Database data are saved into Database whilst file data are saved into session - file) ).
You certainly would not expect to understand all this stuff & moreover without looking at the source code ?