public function setRequestType($requestType)
    {
        $requestType = $this->str($requestType)->caseUpper();

        if (!$requestType->equals('GET') && !$requestType->equals('POST')) {
            throw new OAuth2Exception('Invalid request type provided "' . $requestType->val() . '".
										Possible values are GET and POST.'
            );
        }

        $this->requestType = $requestType->val();
    }