The following is more correct:
$class = get_class($objectToTest);
switch($class) {
    case TreeRequest::class:
        echo "tree request";
        break;
    case GroundRequest::class:
        echo "ground request";
        break;
}
This way namespaces are properly compared (you don’t have to type them out) and if anything changes such as the namespace or class name you’ll get a decent IDE error informing you that your code is broken.