Issue reported by Jim Scherer.

Below is code to demonstrate the failure:

<?php

require_once 'Zend/Loader.php';
Zend_Loader::registerAutoload();

$filters = array( );

$validators = array(
    'test' => array(
        'allowEmpty' => false,
        'fields' => array( 'empty', 'notempty' )
    )
);

$data = array(
    'empty' => '',
    'notempty' => 'not empty'
);

$input = new Zend_Filter_Input( $filters, $validators, $data );

// expect input to be invalid
echo "\ninput->isValid =\n";
var_dump($input->isValid());

echo "\nvalidators =\n";
var_dump($validators);

// echo "\ninput object =\n";
// echo var_dump($input);

echo "\nempty(data[empty]) =\n";
var_dump(empty($data['empty']));

echo "\nempty(data[notempty]) =\n";
var_dump(empty($data['notempty']));