converting php functions that deal with sessions into codeigniter

Question

I have two functions that deal with sessions and i need to convert them into codeigniter way.I managed to do the first one but i am stuck at accessing session array index at the second one

first function:

function addItem($pid,$qty=1){
$_SESSION['basket'][$pid]['kty']=$qty;
}

turned into:

function addItem($pid,$qty=1){
    $arr=array($pid=>array('kty'=>$qty));
        $this->session->set_userdata('basket',$arr);

}

second function:

function removeItem($pid,$qty=null){
        if($qty != null && $qty < $_SESSION['basket'][$pid]['kty']){

        $_SESSION['basket'][$pid]['kty']=($_SESSION['basket'][$pid]['kty']-$qty);
        }else{
        $_SESSION['basket'][$pid]=null;
        unset($_SESSION['basket'][$pid]);
        }

    }

how do i rewrite the second function in codeigniter way?

Answer 1

function removeItem($pid,$qty=null){
        if($qty != null && $qty < $_SESSION['basket'][$pid]['kty']){

        $_SESSION['basket'][$pid]['kty']=($_SESSION['basket'][$pid]['kty']-$qty);
        }else{
        $_SESSION['basket'][$pid]=null;
        unset($_SESSION['basket'][$pid]);
        }

    }

Change $_SESSION TO $this->session->userdata for ex :

$_SESSION['basket'][$pid]['kty'] 
to 
$this->session->userdata['basket'][$pid]['kty']