I assume you are talking about CLIENT SIDE session variables.
These can be accessed via JS, no dependency on Wappler or App Connect.
If you are talking about SERVER SIDE session variables, then you cannot access them in client side in any manner, with or without App Connect.
Only way is the use $_SESSION object in PHP code itself. So that sort of solves your question as well.
It works with query string.
Could you please tell me how can I make post request from app connect client page to non app connect basic php file by using app connect?