src/Auth/SingleUserAuth.php
protected function getSignatureBaseString()
    {
        $method = strtoupper($this->method);

        $url = rawurlencode($this->getUrl());

        return $method . '&' . $url . '&' . $this->getRequestString();
    }
protected function getSignatureBaseString()
    {
        $method = strtoupper($this->method);

        $url = rawurlencode($this->getUrl());

        return $method . '&' . $url . '&' . $this->getRequestString();
    }
Getting OAuth signature base string

@return string  OAuth signature base string