Please go to Eventful API request key page http://api.eventful.com/keys/new , create an application, and in the line 22 set the client_id to oAuth Consumer Key and client_secret with oAuth Consumer Secret. The Callback URL must be http://erp.leaf.com.my/webmail/modules/OAuthIntegratorWebclient/Classes/OAuthClient/login_with_eventful.php