public function checkChars($value)
    {
        if (!is_string($value)) {
            return false;
        }

        $characters = $this->getCharacters();
        if ($characters == 128) {
            for ($x = 0; $x < 128; ++$x) {
                $value = str_replace(chr($x), '', $value);
            }
        } else {
            $chars = str_split($characters);
            foreach ($chars as $char) {
                $value = str_replace($char, '', $value);
            }
        }

        if (strlen($value) > 0) {
            return false;
        }

        return true;
    }