the session variable name to use may be different. to determine what the correct session variable name is, open the security assist login page and double click the security assist authenticate user server behavior, on the third page the session variables will be listed, make note of the session variable name for the ID column.
If this session variable is not listed on the bindings panel, you can add it manually. on the bindings panel, click the plus button and select Session Variable, then type the name for the user ID session variable.
NOTE: PHP is case sensitive, when adding the binding, make sure to use the correct case.