Search on phone number in AD

Is it possible to search in LDAP who has their phonenumber set? (as in, everybody without开发者_开发技巧 a NULL value as phone will be shown?)

edit: without knowing the usernames beforehand..

Figured it out myself by playing around abit, for any1 curious:

$filter = '(&(objectCategory=person)(telephoneNumber=*))';

Does the trick