Error authenticating user on Codeigniter Rest Server

Error authenticating user on Codeigniter Rest Server

I am using Phil Sturgeon's Codeginiter Rest Server to create RESTful API.
I changed this line in config/rest.php
$config['rest_auth'] = '';
to
$config['rest_auth'] = 'digest';
and made a user in the line,
$config['rest_valid_logins'] = array( 'username' => 'password', 'test' =>
'secure123' );
Whenever I try to enter the username & password, I get the error,
Message: ldap_bind() [function.ldap-bind]: Unable to bind to server: Can't
contact LDAP server
Filename: libraries/REST_Controller.php
Line Number: 1026
and this one,
Message: Cannot modify header information - headers already sent by
(output started at
/Users/user/Documents/workspace/restdev/system/core/Exceptions.php:185)
Filename: libraries/REST_Controller.php
Line Number: 1238
One more thing to note I am using Mac OS X.
What I might be doing wrong? Any suggestions?