[PHP Lib]When ordering by field only return results that have a value in field

Hello,

I've been trying to figure out how best to implement this.

I'd like to add a new field A. A will contain a numeric value. When sorting by A I would like to avoid record that have no value in A from appearing. I haven't been able to find anything in the PHP library's API that seems to achieve this cleanly.

Any help is appreciated!