src/Core/HttpClients/SyncRestHandler.php
private function getOAuth2AuthorizationHeader($OAuth2AccessToken){
      if(!$OAuth2AccessToken instanceof OAuth2AccessToken){
         throw new SdkException("Internal Error. The OAuth 2 configuration is not complete.");
      }

      $accessToken = $OAuth2AccessToken->getAccessToken();
      $AuthorizationHeader = "Bearer " . $accessToken;
      return $AuthorizationHeader;
    }
private function getOAuth2AuthorizationHeader($OAuth2AccessToken){
      if(!$OAuth2AccessToken instanceof OAuth2AccessToken){
         throw new SdkException("Internal Error. The OAuth 2 configuration is not complete.");
      }

      $accessToken = $OAuth2AccessToken->getAccessToken();
      $AuthorizationHeader = "Bearer " . $accessToken;
      return $AuthorizationHeader;
    }
Get OAuth2 Authroization Header based on OAuth 2 Access Token

@param OAuth2AccessToken   $OAuth2AccessToken     The OAuth 2 token contains AccessToken, RefreshToken, ClientID and Client Secret.
@return string OAuth2 Authorization Header