Codeigniter Application with LDAP Authentication

Without codeigniter i am able to connect to ldap_connect but in my codeigniter project i want to embed ldap connectivity also.

the following are the scenarios

1. If the username and email id exist in database then it is connected to ldap using ldap_connect() and get the windows login password and then validate.(Note: the users with username, mail id and windows login password)
2. if username and password exist in database it will be validated and loggedin.(the users with username and no windows login password or mail id)

i did it without codeigniter but here i don't know how to use ldap
Sample code:

PHP Code:

/******LDAP CONNECTIVITY STARTS HERE*********/
$ldaprdn = $_POST['uname']; // ldap rdn or dn
    $ldappass = $_POST['upass']; // associated password
    $ldaprdn = $_POST['uname'].'@domain.com';
    $ldapconn = ldap_connect("ip") or die("Could not connect to LDAP server."); //our ip
if ($ldapconn) {
    $ldapbind = ldap_bind($ldapconn, $ldaprdn, $ldappass);
        // verify binding
        if ($ldapbind) {
            //echo "<pre>";
            //print_r($row_login);
            //exit;

            $_SESSION['appusername']=$_POST['uname'];
            $_SESSION['emp_code']=$row_login['emp_code'];
            $_SESSION['emp_id']=$row_login['emp_id'];
            $_SESSION['emp_name']=$row_login['emp_name'];
            $_SESSION['emp_email']=$row_login['emp_email'];
            $_SESSION['emp_dept_id']=$row_login['emp_dept_id'];
            $_SESSION['emp_dept_name']=$row_login['dept_name'];
            $_SESSION['emp_group']=$row_login['emp_group'];
            $_SESSION['emp_category']=$row_login['emp_category'];

            $_SESSION['finance_app_authority']=$row_login['finance_approval_status'];
            $_SESSION['line_eng_status']=$row_login['line_eng_status'];

            $_SESSION['line_name']=$row_login['line_name'];
            $_SESSION['dept_name']=$row_login['dept_name'];

            if($row_login['emp_mod_status']=='Y'){ //if moderator means
                $_SESSION['userType']='MOD';
            }
            else if($row_login['emp_id']==$row_login['dept_hod_id']){ //if HOD means
                $_SESSION['userType']='HOD';
            }else{ //if normal user means
                $_SESSION['userType']='EMP';
            }
            echo '<script language="javascript">document.location.href="?p=main&m=it-home"</script>';
            exit;

        }
        else{
        echo '<div  class="man_style" style="width:50%;padding:10px 10px 10px 250px !important;text-align:center;color:red;">Invalid password.</div>';
        }
    } 


Stackoverflow URL : http://stackoverflow.com/questions/29224...entication
Your help is appreciated