src/Core/Configuration/LocalConfigReader.php
public static function initializeOAuthSettings($xmlObj, $ippConfig, $OAuthOption)
   {

         // if it is OAuth1 Settings.
         if (isset($xmlObj) &&
                 isset($xmlObj->intuit->ipp->security) &&
                 $OAuthOption == CoreConstants::OAUTH1  &&
                 isset($xmlObj->intuit->ipp->security->oauth1)) {
             try {
                 $currentAccessTokenKey = $xmlObj->intuit->ipp->security->oauth1->attributes()['accessTokenKey'];
                 $currentAccessTokenSecret = $xmlObj->intuit->ipp->security->oauth1->attributes()['accessTokenSecret'];
                 $currentConsumerKey = $xmlObj->intuit->ipp->security->oauth1->attributes()['consumerKey'];
                 $currentConsumerSecret =    $xmlObj->intuit->ipp->security->oauth1->attributes()['consumerSecret'];
                 $ippConfig->RealmID =  $xmlObj->intuit->ipp->security->oauth1->attributes()['QBORealmID'];
                 $ippConfig->OAuthMode = CoreConstants::OAUTH1;
             } catch (\Exception $e) {
                 throw new \Exception("Can't Read OAuth1 values from config file.");
             }
             $ippConfig->Security = new OAuthRequestValidator($currentAccessTokenKey, $currentAccessTokenSecret, $currentConsumerKey, $currentConsumerSecret);
         }
         // OAUth 2 settings if available
         elseif (isset($xmlObj) &&
                 isset($xmlObj->intuit->ipp->security) &&
                 $OAuthOption == CoreConstants::OAUTH2  &&
                 isset($xmlObj->intuit->ipp->security->oauth2)) {
             //Implement OAuth 2 parts here
            // Set SSL check status to be true
            $ippConfig->SSLCheckStatus = true;
            $currentOAuth2AccessTokenKey = $xmlObj->intuit->ipp->security->oauth2->attributes()['accessTokenKey'];
            $currentOAuth2RefreshTokenKey = $xmlObj->intuit->ipp->security->oauth2->attributes()['refreshTokenKey'];
            $clientID = $xmlObj->intuit->ipp->security->oauth2->attributes()['ClientID'];
            $clientSecret =    $xmlObj->intuit->ipp->security->oauth2->attributes()['ClientSecret'];
            $ippConfig->RealmID =  $xmlObj->intuit->ipp->security->oauth2->attributes()['QBORealmID'];
            $OAuth2AccessToken = new OAuth2AccessToken($clientID, $clientSecret, $currentOAuth2AccessTokenKey, $currentOAuth2RefreshTokenKey);

            $ippConfig->Security = $OAuth2AccessToken;
            $ippConfig->OAuthMode = CoreConstants::OAUTH2;
         } else {
             throw new \Exception("Can't load " .$OAuthOption .  " config from config file or the OAuth option is not supported.");
         }
   }
public static function initializeOAuthSettings($xmlObj, $ippConfig, $OAuthOption)
   {

         // if it is OAuth1 Settings.
         if (isset($xmlObj) &&
                 isset($xmlObj->intuit->ipp->security) &&
                 $OAuthOption == CoreConstants::OAUTH1  &&
                 isset($xmlObj->intuit->ipp->security->oauth1)) {
             try {
                 $currentAccessTokenKey = $xmlObj->intuit->ipp->security->oauth1->attributes()['accessTokenKey'];
                 $currentAccessTokenSecret = $xmlObj->intuit->ipp->security->oauth1->attributes()['accessTokenSecret'];
                 $currentConsumerKey = $xmlObj->intuit->ipp->security->oauth1->attributes()['consumerKey'];
                 $currentConsumerSecret =    $xmlObj->intuit->ipp->security->oauth1->attributes()['consumerSecret'];
                 $ippConfig->RealmID =  $xmlObj->intuit->ipp->security->oauth1->attributes()['QBORealmID'];
                 $ippConfig->OAuthMode = CoreConstants::OAUTH1;
             } catch (\Exception $e) {
                 throw new \Exception("Can't Read OAuth1 values from config file.");
             }
             $ippConfig->Security = new OAuthRequestValidator($currentAccessTokenKey, $currentAccessTokenSecret, $currentConsumerKey, $currentConsumerSecret);
         }
         // OAUth 2 settings if available
         elseif (isset($xmlObj) &&
                 isset($xmlObj->intuit->ipp->security) &&
                 $OAuthOption == CoreConstants::OAUTH2  &&
                 isset($xmlObj->intuit->ipp->security->oauth2)) {
             //Implement OAuth 2 parts here
            // Set SSL check status to be true
            $ippConfig->SSLCheckStatus = true;
            $currentOAuth2AccessTokenKey = $xmlObj->intuit->ipp->security->oauth2->attributes()['accessTokenKey'];
            $currentOAuth2RefreshTokenKey = $xmlObj->intuit->ipp->security->oauth2->attributes()['refreshTokenKey'];
            $clientID = $xmlObj->intuit->ipp->security->oauth2->attributes()['ClientID'];
            $clientSecret =    $xmlObj->intuit->ipp->security->oauth2->attributes()['ClientSecret'];
            $ippConfig->RealmID =  $xmlObj->intuit->ipp->security->oauth2->attributes()['QBORealmID'];
            $OAuth2AccessToken = new OAuth2AccessToken($clientID, $clientSecret, $currentOAuth2AccessTokenKey, $currentOAuth2RefreshTokenKey);

            $ippConfig->Security = $OAuth2AccessToken;
            $ippConfig->OAuthMode = CoreConstants::OAUTH2;
         } else {
             throw new \Exception("Can't load " .$OAuthOption .  " config from config file or the OAuth option is not supported.");
         }
   }
Initialize OAuth Settings from Simple XML Reading from SDK.config or specific file
rightnow the default OAuth module is OAuth 1.
@Hao