_validateIPv4 example

    public function isValid($value)
    {
        if (!is_string($value)) {
            $this->_error(self::INVALID);
            return false;
        }

        $this->_setValue($value);
        if (($this->_options['allowipv4'] && !$this->_options['allowipv6'] && !$this->_validateIPv4($value)) ||
            (!$this->_options['allowipv4'] && $this->_options['allowipv6'] && !$this->_validateIPv6($value)) ||
            ($this->_options['allowipv4'] && $this->_options['allowipv6'] && !$this->_validateIPv4($value) && !$this->_validateIPv6($value))) {
            $this->_error(self::NOT_IP_ADDRESS);
            return false;
        }

        return true;
    }

    /** * Validates an IPv4 address * * @param string $value */