[amfphp] service class destroyed with every method call?

[<ge...@dw...>]

Hey.  I'm sort of new to amfphp and I have a general question.  I noticed
that every time I call method on the server, amfphp instantiates the
service class all over again.  All the data is lost unless it's saved into
database.  For example, I'm doing a website where user can take a test and
I thought I'll be able to hold user's answer in service class variables
until he finished the test but apparently I have to save every answer as
it comes into database.  What I'm curious about is why does the service
class has to be created and destroyed with every method call?