Class mapping in ZendAMF - actually useless?

Question

Some concerns about ZendAMF....

one question about ZendAMF and the integration of Flex (AS3) with PHP5. What is the sense of definining Value Objects in PHP and perform all the explicit class mapping with AS3 classes, when type checking is not enforced anyways?

Example: I create a Contact object in PHP, add some non-member variables and send it via ZendAMF to Flex. There it will still be recognised as a valid Contact object.

In addition, the setClassMapping method does not care if the Flex and PHP Object actually looks alike.

Is there a function, which checks if an object really only defines member defined in the class (PHP and AS3)?

Otherwise I dont understand the whole concept of binding the classes, when I am anyways able to send whatever I want an the serialized object will comply (whatsoever it contains) as a valid object.

Thanks, Martin