getState(); if ($requestState === Request::EMPTY_REQUEST) { // code to handle empty request } elseif ($requestState === Request::SUCCESS) { // code to handle successful request } elseif ($requestState === Request::BAD_REQUEST) { // code to handle bad request (e.g. missing required parameters) } elseif ($requestState === Request::ERROR) { // code to handle errors (e.g. network issues) } elseif ($requestState === Request::AUTHENTICATION_FAILED) { // code to handle authentication failure } else { // code to handle unknown state } ?>The getState() method is commonly used in package libraries for implementing RESTful API services. These libraries can be available as open-source libraries or as part of other PHP frameworks, such as Symfony or Laravel.