protected function _validatePhrase($phrase)
    {
        // Splits on one or more Tab or space.
        $parts = preg_split('/[ \\x09]+/', $phrase, -1, PREG_SPLIT_NO_EMPTY);

        $phrase_parts = array();
        while (count($parts) > 0){
            $phrase_parts[] = $this->_splitCheck($parts, ' ');
            for ($i = 0; $i < $this->index + 1; $i++)
                array_shift($parts);
        }

        foreach ($phrase_parts as $part) {
            // If quoted string:
            if (substr($part, 0, 1) == '"') {
                if (!$this->_validateQuotedString($part)) {
                    return false;
                }
                continue;
            }

            // Otherwise it's an atom:
            if (!$this->_validateAtom($part)) return false;
        }

        return true;
    }