Extending Zend_Filter_PregReplace like the following code will throw fatal error "does not have a valid MatchPattern set". Passing null as options to the constrcutor should not set matchPattern property to NULL, while this property is set in the child class

require_once 'Zend/Filter/PregReplace.php';

class Ms_View_Filter_LinkArrows extends Zend_Filter_PregReplace{
     
    /**
     * Pattern to match
     * @var mixed
     */
    protected $_matchPattern = array('~(>){3,}~i');

    /**
     * Replacement pattern
     * @var mixed
     */
    protected $_replacement = ' ';

}