php ldap_search Operations error

Question

I want to use the following php script to retrieve AD Users (Windows 2008R2) who have the "proxyAddresses" attribute set:

<?php
$ldaprdn  = 'ldapbind@test.net';
$ldappass = 'testpass';

$ldapconn = ldap_connect("ldap://10.1.20.254:389")
    or die("Could not connect to LDAP server.");

ldap_set_option($ldapconn, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($ldapconn, LDAP_OPT_REFERRALS, 0);

if ($ldapconn) {
    $ldapbind = ldap_bind($ldapconn, $ldaprdn, $ldappass); 
    if ($ldapbind) {
        echo "LDAP bind successful...\n";
        $result = ldap_search($ldapconn, "CN=Users,DN=test,DN=net", "(proxyAddresses=*)")
        or die ("Error in serach query: " . ldap_error($ldapconn));
        $data = ldap_get_entries($ldapconn, $result);
        print_r($data);
    } else {
        echo "LDAP bind failed...";
    }
}
?>

It binds successful, but then i get warning and error message:

PHP Warning:  ldap_search() Operations error in ..... on line .. (the ldap_search line)

and

Error in search query: Operations error

When i execute an ldapsearch on the console:

ldapsearch -h 10.1.20.254 -p 389 -D 'ldapbind@test.net' -w 'testpass' -b 'CN=Users,DC=test,DC=net' '(proxyAddresses=*)' cn proxyAddresses mail

i get the desired results.

It's running on "CentOS release 6.4 (Final).

Thanks in advance