PHP: Get user list from the Active Directory

/**
 * Get a list of users from Active Directory.
 */
$ldap_password = 'PASSWORD';
$ldap_username = 'USERNAME@DOMAIN';
$ldap_connection = ldap_connect(HOSTNAME);
if (FALSE === $ldap_connection){
    // Uh-oh, something is wrong...
}

// 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)){
    $ldap_base_dn = 'DC=XXXX,DC=XXXX';
    $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){
        $entries = ldap_get_entries($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";