PHP：返回Laravel 4中更新行的ID

I am trying to return the last updated ID in my Laravel application. I have a payment inserted into the database. When there is refund from PayPal the IPN will update the payment_status to "Refunded". Now after updating this needs to return the id of the updated column. But I am getting null. Here is what I have tried.

1st method:

    $is_updated = $this->whereTxnId($ipn_array['parent_txn_id'])
    ->update(array(
        'payment_status' => $ipn_array['payment_status'],
        'refund_txn_id' => $ipn_array['txn_id']
    ));
if($is_updated) {
    return $this->id;
}

2nd method:

$txn_id_matching = $this->whereTxnId($ipn_array['parent_txn_id']);

$txn_id_matching->payment_status = $ipn_array['payment_status'];
$txn_id_matching->refund_txn_id = $ipn_array['txn_id'];
$is_updated = $txn_id_matching->save();

if($is_updated) {
    return $txn_id_matching->id;
}

How can I retrieve the updated id?

I fixed it using the below code. I do not know if this code is efficient but it fixed my issue.

public function unlockIpnUpdate($ipn_array) {

        $is_updated = $this->whereTxnId($ipn_array['parent_txn_id'])
            ->update(array(
                'payment_status' => $ipn_array['payment_status'],
                'refund_txn_id' => $ipn_array['txn_id']
            ));

        $txn_id_matching = $this->whereTxnId($ipn_array['parent_txn_id'])->first();

        if($is_updated) {
            return $txn_id_matching->id;
        }

        return false;

    }

With your second method use

$is_updated->id