Get post data, Zend Framework

I want to fetch posted data. But I am using no form. The data is postet by a jquery script with method post and I would like to fetch it.

I know how to fetch parameters

$id = $this->getRequest ()->getParam ( 'id', null );

and form values

$message = $form->getValue ( 'message' );

however I want to access post data and not parameters or form values. Any ideas?