im re-factoring php on zend code and all the code is full of $_GET[\"this\"] and $_POST[\"that\"]. I have always used the more phpish $this->_
You can't write a one-size-fits-all validation function for get/post data. As in some cases you require a field to be a integer and in others a date for instance. That's why there is no input validation in the zend framework.
You will have to write the validation code at the place where you need it. You can of course write some helper methods, but you can't expect the getPost() to validate something for you all by itself...
And it isn't even getPost/getQuery's place to validate anything, it's job is to get you the data you wan't, what happens to it from there on should not be it's concern.