“此集合实例laravel上不存在属性[left_b]？

Question

i want to insert data only in 3 rows .

i have tried

$currentBV = MemberExtra::where('user_id', $posid)->limit(3)->get();

but getting following error

"Property [left_b] does not exist on this collection instance

here is full code of function:

function updateDepositBV($id, $deposit_amount)
{
    while($id !="" || $id != "0") {
        if(isMemberExists($id))
        {
            $posid = getParentId($id);
            if($posid == "0")
                break;
            $position = getPositionParent($id);

 $currentBV = MemberExtra::where('user_id', $posid)->limit(3)->get();


            if($position == "R"){
                $new_lbv = $currentBV->left_bv ;
                $new_rbv = $currentBV->right_bv + request()->input('lend_amount');