PHP LDAP не может найти пользователя

Я могу успешно подключаться и связываться с LDAP, и я могу запрашивать пользователей с одного уровня домена, но не пользователей с следующего уровня ниже.

База дн я могу запросить:

$ldap_base_dn = 'DC=a_level,DC=company,DC=org';

База дн я хотел бы запросить:

$ldap_base_dn = 'DC=b_level,DC=a_level,DC=company,DC=org';

Я связываюсь с LDAP, используя учетную запись администратора.

<?php

/**
* Get a list of users from Active Directory.
*/
$ldap_password = 'PASSWORD';
$ldap_username = 'ADMIN';
$ldap_connection = ldap_connect('ldap://ldap.company.org/');
if (false === $ldap_connection) {
// Uh-oh, something is wrong...
print "CONNECT ERROR<br />";
}

// We have to set this option for the version of Active Directory we are using.
ldap_set_option($ldap_connection, LDAP_OPT_PROTOCOL_VERSION, 3) or die('Unable to set LDAP protocol version');
ldap_set_option($ldap_connection, LDAP_OPT_REFERRALS, 0); // We need this for doing an LDAP search.

if (true === ldap_bind($ldap_connection, $ldap_username, $ldap_password)) {
print "ldap bind<br />";
$ldap_base_dn = 'DC=b_level,DC=a_level,DC=company,DC=org';
$search_filter = '(&(objectCategory=person)(samaccountname=*))';
$attributes = array();
$attributes[] = 'givenname';
$attributes[] = 'mail';
$attributes[] = 'samaccountname';
$attributes[] = 'sn';
$result = ldap_search($ldap_connection, $ldap_base_dn, $search_filter, $attributes);
if (false !== $result) {
print "ldap search<br />";
$entries = ldap_get_entries($ldap_connection, $result);
for ($x=0; $x<$entries['count']; $x++) {
if (!empty($entries[$x]['givenname'][0]) &&
!empty($entries[$x]['mail'][0]) &&
!empty($entries[$x]['samaccountname'][0]) &&
!empty($entries[$x]['sn'][0]) &&
'Shop' !== $entries[$x]['sn'][0] &&
'Account' !== $entries[$x]['sn'][0]) {
$ad_users[strtoupper(trim($entries[$x]['samaccountname'][0]))] = array('email' => strtolower(trim($entries[$x]['mail'][0])),'first_name' => trim($entries[$x]['givenname'][0]),'last_name' => trim($entries[$x]['sn'][0]));
}
}
}
ldap_unbind($ldap_connection); // Clean up after ourselves.
}

$message .= "Retrieved ". count($ad_users) ." Active Directory users\n";

print $message;

echo '<pre>';
print_r($entries);
echo '</pre>';

Используя программу Apache Directory studio, я могу запустить поиск пользователя в b_level и в базе поиска dn, поэтому я не понимаю, почему не работает версия php.

РЕДАКТИРОВАТЬ:

Внесены изменения для отображения ошибок вывода.

<?php

/**
* Get a list of users from Active Directory.
*/
$ldap_password = 'PASSWORD';
$ldap_username = 'ADMIN';
$ldap_connection = ldap_connect('ldap://ldap.company.org/');
if (false === $ldap_connection) {
// Uh-oh, something is wrong...
print "CONNECT ERROR<br />";
}

print "Connect Success...<br />";

// We have to set this option for the version of Active Directory we are using.
ldap_set_option($ldap_connection, LDAP_OPT_PROTOCOL_VERSION, 3) or die('Unable to set LDAP protocol version');
ldap_set_option($ldap_connection, LDAP_OPT_REFERRALS, 0); // We need this for doing an LDAP search.

if (true === ldap_bind($ldap_connection, $ldap_username, $ldap_password)) {
print "Bind Success...<br />";
$ldap_base_dn = 'DC=b_level,DC=a_level,DC=company,DC=org';
$search_filter = '(&(objectCategory=person)(samaccountname=*))';
$attributes = array();
$attributes[] = 'givenname';
$attributes[] = 'mail';
$attributes[] = 'samaccountname';
$attributes[] = 'sn';
$result = ldap_search($ldap_connection, $ldap_base_dn, $search_filter, $attributes);
print "ldap_search error: ".ldap_error($ldap_connection) . '<br />';
if (false !== $result) {
print "LDAP Search...<br />";
$entries = ldap_get_entries($ldap_connection, $result);
for ($x=0; $x<$entries['count']; $x++) {
if (!empty($entries[$x]['givenname'][0]) &&
!empty($entries[$x]['mail'][0]) &&
!empty($entries[$x]['samaccountname'][0]) &&
!empty($entries[$x]['sn'][0]) &&
'Shop' !== $entries[$x]['sn'][0] &&
'Account' !== $entries[$x]['sn'][0]) {
$ad_users[strtoupper(trim($entries[$x]['samaccountname'][0]))] = array('email' => strtolower(trim($entries[$x]['mail'][0])),'first_name' => trim($entries[$x]['givenname'][0]),'last_name' => trim($entries[$x]['sn'][0]));
}
}
}
ldap_unbind($ldap_connection); // Clean up after ourselves.
}

$message .= "Retrieved ". count($ad_users) ." Active Directory users\n";

print $message;

echo '<pre>';
print_r($entries);
echo '</pre>';

вывод:

Connect Success...
Bind Success...
ldap_search error: Referral
LDAP Search...
Retrieved 0 Active Directory users
Array
(
[count] => 0
)