ldap_search filter with memberOf

["Zaitchik, Alan" <Alan.Zaitchik@xxxxxxxxxxxx>]

I am trying to construct a filter for ldap_search that tests the AD memberOf attribute. The latter has possibly multiple values for a given user, and I want something like (memberOf=*Student*) to get all and only the students. I realize that the above does not work, that the memberOf attribute has some internal structure that requires something more complicated, but I cannot seem to get it working.

What I have done is use a very broad $filter, an $attribs that includes "memberOf"-- and then loop through the results keeping only the students, thus:

$sr= ldap_search($ldapconn, $dn, $filter, $attribs);

for ($entryid=ldap_first_entry($ldapconn,$sr);$entryid!=false;$entryid=ldap_next_entry($ldapconn,$entryid)){

                $this_memberof = implode(ldap_get_values($ldapconn,$entryid,'memberof'));

                If (stripos($this_memberof,'student') ) {

                                // do something, etc.

}

}

But this is wildly inefficient. How can I just create the filter I need for ldap_search? 

Thanks!

Alan