session_module_name gets the name of the current session module, which is also known as session.save_handler.
If module is specified and not null, that module will be used instead. Passing "user" to this parameter is forbidden. Instead session_set_save_handler has to be called to set a user defined session handler.
Returns the name of the current session module, or false on failure.
|8.0.0||module is nullable now.|
|7.2.0||It is now explicitly forbidden to set the module name to "user". Formerly, this has been silently ignored.|