src/Zend/Filter/Null.php
public function setType($type = null)
    {
        if (is_array($type)) {
            $detected = 0;
            foreach($type as $value) {
                if (is_int($value)) {
                    $detected += $value;
                } else if (in_array($value, $this->_constants)) {
                    $detected += array_search($value, $this->_constants);
                }
            }

            $type = $detected;
        } else if (is_string($type)) {
            if (in_array($type, $this->_constants)) {
                $type = array_search($type, $this->_constants);
            }
        }

        if (!is_int($type) || ($type < 0) || ($type > self::ALL)) {

            throw new Zend_Filter_Exception('Unknown type');
        }

        $this->_type = $type;
        return $this;
    }
public function setType($type = null)
    {
        if (is_array($type)) {
            $detected = 0;
            foreach($type as $value) {
                if (is_int($value)) {
                    $detected += $value;
                } else if (in_array($value, $this->_constants)) {
                    $detected += array_search($value, $this->_constants);
                }
            }

            $type = $detected;
        } else if (is_string($type)) {
            if (in_array($type, $this->_constants)) {
                $type = array_search($type, $this->_constants);
            }
        }

        if (!is_int($type) || ($type < 0) || ($type > self::ALL)) {

            throw new Zend_Filter_Exception('Unknown type');
        }

        $this->_type = $type;
        return $this;
    }
Set the null types

@param  integer|array $type
@throws Zend_Filter_Exception
@return Zend_Filter_Null