yii\authclient\OAuthToken::getParams PHP Method

    public function getParams()
    {
        return $this->_params;
    }

 /**
  * Gets new auth token to replace expired one.
  * @param OAuthToken $token expired auth token.
  * @return OAuthToken new auth token.
  */
 public function refreshAccessToken(OAuthToken $token)
 {
     $params = ['client_id' => $this->clientId, 'client_secret' => $this->clientSecret, 'grant_type' => 'refresh_token'];
     $params = array_merge($token->getParams(), $params);
     $response = $this->sendRequest('POST', $this->tokenUrl, $params);
     return $response;
 }