`group` needs to be added early because it needs to be the first key. If I do it after the `options` processing, then I'll need to collect the `maxTimeMS` option (basically run `zend_hash_find()` and do nothing on success/failure), and then add the option into `cmd` later.

Initializing `cmd` and adding `group` early didn't seem like it'd cause a problem, as I assumed `add_assoc_zval()` just links the value in and doesn't do any copying.