use \GuzzleHttp\Exception\ClientException; try { // Some code that may throw a ClientException } catch (ClientException $e) { // Handle the 404 error by rendering a custom error page $app->get('/error/404', function () use ($app) { $app->render('error/404.php'); }); }In this example, the `try` block contains some code that may throw a `ClientException`, which is a type of error that can occur when a user tries to navigate to a page that does not exist. The `catch` block handles this error by rendering a custom 404 error page using the `Route ErrorPage404` feature. This feature is typically included as part of a PHP framework or library, such as Laravel or Slim Framework, which provide routing functionality and other web development tools.