OAuth2\OAuth2::grantAccessToken PHP Method

    public function grantAccessToken(Request $request = null)
    {
        $filters = array("grant_type" => array("filter" => FILTER_VALIDATE_REGEXP, "options" => array("regexp" => self::GRANT_TYPE_REGEXP), "flags" => FILTER_REQUIRE_SCALAR), "scope" => array("flags" => FILTER_REQUIRE_SCALAR), "code" => array("flags" => FILTER_REQUIRE_SCALAR), "redirect_uri" => array("filter" => FILTER_SANITIZE_URL), "username" => array("flags" => FILTER_REQUIRE_SCALAR), "password" => array("flags" => FILTER_REQUIRE_SCALAR), "refresh_token" => array("flags" => FILTER_REQUIRE_SCALAR));
        if ($request === null) {
            $request = Request::createFromGlobals();
        }
        // Input data by default can be either POST or GET
        if ($request->getMethod() === 'POST') {
            $inputData = $request->request->all();
        } else {
            $inputData = $request->query->all();
        }
        // Basic authorization header
        $authHeaders = $this->getAuthorizationHeader($request);
        // Filter input data
        $input = filter_var_array($inputData, $filters);
        // Grant Type must be specified.
        if (!$input["grant_type"]) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_REQUEST, 'Invalid grant_type parameter or parameter missing');
        }
        // Authorize the client
        $clientCredentials = $this->getClientCredentials($inputData, $authHeaders);
        $client = $this->storage->getClient($clientCredentials[0]);
        if (!$client) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_CLIENT, 'The client credentials are invalid');
        }
        if ($this->storage->checkClientCredentials($client, $clientCredentials[1]) === false) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_CLIENT, 'The client credentials are invalid');
        }
        if (!$this->storage->checkRestrictedGrantType($client, $input["grant_type"])) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_UNAUTHORIZED_CLIENT, 'The grant type is unauthorized for this client_id');
        }
        // Do the granting
        switch ($input["grant_type"]) {
            case self::GRANT_TYPE_AUTH_CODE:
                // returns array('data' => data, 'scope' => scope)
                $stored = $this->grantAccessTokenAuthCode($client, $input);
                break;
            case self::GRANT_TYPE_USER_CREDENTIALS:
                // returns: true || array('scope' => scope)
                $stored = $this->grantAccessTokenUserCredentials($client, $input);
                break;
            case self::GRANT_TYPE_CLIENT_CREDENTIALS:
                // returns: true || array('scope' => scope)
                $stored = $this->grantAccessTokenClientCredentials($client, $input, $clientCredentials);
                break;
            case self::GRANT_TYPE_REFRESH_TOKEN:
                // returns array('data' => data, 'scope' => scope)
                $stored = $this->grantAccessTokenRefreshToken($client, $input);
                break;
            default:
                if (substr($input["grant_type"], 0, 4) !== 'urn:' && !filter_var($input["grant_type"], FILTER_VALIDATE_URL)) {
                    throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_REQUEST, 'Invalid grant_type parameter or parameter missing');
                }
                // returns: true || array('scope' => scope)
                $stored = $this->grantAccessTokenExtension($client, $inputData, $authHeaders);
        }
        if (!is_array($stored)) {
            $stored = array();
        }
        // if no scope provided to check against $input['scope'] then application defaults are set
        // if no data is provided than null is set
        $stored += array('scope' => $this->getVariable(self::CONFIG_SUPPORTED_SCOPES, null), 'data' => null, 'access_token_lifetime' => $this->getVariable(self::CONFIG_ACCESS_LIFETIME), 'issue_refresh_token' => true, 'refresh_token_lifetime' => $this->getVariable(self::CONFIG_REFRESH_LIFETIME));
        $scope = $stored['scope'];
        if ($input["scope"]) {
            // Check scope, if provided
            if (!isset($stored["scope"]) || !$this->checkScope($input["scope"], $stored["scope"])) {
                throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_SCOPE, 'An unsupported scope was requested.');
            }
            $scope = $input["scope"];
        }
        $token = $this->createAccessToken($client, $stored['data'], $scope, $stored['access_token_lifetime'], $stored['issue_refresh_token'], $stored['refresh_token_lifetime']);
        return new Response(json_encode($token), 200, $this->getJsonHeaders());
    }

 /**
  * @param  Request $request
  * @return type
  */
 public function tokenAction(Request $request)
 {
     try {
         return $this->server->grantAccessToken($request);
     } catch (OAuth2ServerException $e) {
         return $e->getHttpResponse();
     }
 }