ZF-9414: Zend_Filter_Input should probably implement Zend_Validate_Interface


As far as it's used (probably even more often than for filtering) for validation it should implement Zend_Validate_Interface. It does implement it already, you only need to add 'implements Zend_Validate_Interface'.


Actually, it doesn't fully implement Zend_Validate_Interface. Zend_Validate_Interface::isValid() expects a value; Zend_Filter_Input::isValid() makes that value optional, which breaks the contract.