Having this filter definition established provides the foundation
Zend_Filter_Interface, which requires a single
filter() to be implemented by a filter
Following is a basic example of using a filter upon two input data, the ampersand (&) and double quote (") characters:
$htmlEntities = new Zend_Filter_HtmlEntities();
echo $htmlEntities->filter('&'); // &
echo $htmlEntities->filter('"'); // "