public function isConditionalClause($string) {
        $matched= false;
        if (is_string($string)) {
            if (!static::isValidClause($string)) {
                throw new xPDOException("SQL injection attempt detected: {$string}");
            }
            foreach ($this->_operators as $operator) {
                if (strpos(strtoupper($string), $operator) !== false) {
                    $matched= true;
                    break;
                }
            }
        }
        return $matched;
    }