Please go to Google APIs console page http://code.google.com/apis/console in the API access tab, create a new client ID, and in the line 22 set the client_id to Client ID and client_secret with Client Secret. The callback URL must be https://erp.leaf.com.my/webmail/modules/OAuthIntegratorWebclient/Classes/OAuthClient/google_contacts_api_php_example.php but make sure the domain is valid and can be resolved by a public DNS.