退还已获取的授权

Question

am using the php api sdk found here: https://github.com/paypal/PayPal-PHP-SDK but am having trouble issuing a refund.

This is the code I am using:

// CAPTURE THE ORIGINAL AUTHORIZATION
try
{
    $amount = new Amount();
    $amount->setCurrency("USD");
    $amount->setTotal($amount_authorized);

    $capture = new Capture();
    $capture->setId($authorization_id);
    $capture->setAmount($amount);

    $authorization = Authorization::get($transaction_id, $apiContext);
    $capt = $authorization->capture($capture, $apiContext);

    if ($capt->state == 'completed')
    {
        $capture_id = $capt->id;
    }
}
catch (PayPal\Exception\PayPalConnectionException $e)
{
    $response = json_decode($e->getData());
    die('Error capturing funds: '.$response->message);
}
catch (Exception $e)
{
    die('Error capturing funds: '.$e->getMessage());
}

// REFUND THE CAPTURE
try
{
    $amount = new Amount();
    $amount->setCurrency("USD");
    $amount->setTotal($refund_amount);

    $refund = new Refund();
    $refund->setId($capture_id);
    $refund->setAmount($amount);

    $capture = Capture::get($capture_id, $apiContext);
    $captureRefund = $capture->refund($refund, $apiContext);

    if ($captureRefund->state == 'completed')
    {
        die('REFUNDED');
    }
}
catch (PayPal\Exception\PayPalConnectionException $e)
{
    $response = json_decode($e->getData());
    die('There was an error refunding the funds: '.$response->message);
}
catch (Exception $e)
{
    die('There was an error refunding the funds: '.$e->getMessage());
}

I get this error everytime: The requested resource ID was not found

I believe I am following the sample code on the developer site but I'll pulling my hair out. It's probably something pretty easy I hope.

Any ideas?

Thanks