在支付给买家帐户时，没有获得paypal交易ID作为回报网址

Question

当我向pay-pal商业帐户付款时，我获得了交易ID（tx）＆amp;返回URL中的付款状态（st）。但是当我向买家/个人账户付款时，我没有得到任何回复网址。

// paypal.php（$ ll_pp_email将成为买家电子邮件ID）

$this_script = BASE_URL.'admin/ukorder/paypal';
$this->paypal_class->add_field('business', $ll_pp_email);
$this->paypal_class->add_field('cmd', '_xclick');
$this->paypal_class->add_field('upload', '1');
$this->paypal_class->add_field('amount', $landlord_amount);
$this->paypal_class->add_field('item_name', this->input->post('prop_title'));
$this->paypal_class->add_field('return', $this_script.'/success');
$this->paypal_class->add_field('cancel_return', $this_script.'/cancel');
$this->paypal_class->add_field('notify_url', $this_script.'/ipn');
$this->paypal_class->add_field('currency_code', 'GBP');
$this->paypal_class->add_field('invoice', $invoice);
$this->paypal_class->add_field('email', ADMIN_EMAIL_ADD);
$this->paypal_class->submit_paypal_post($sandbox);

//成功

if(!empty($_GET['st']) && !empty($_GET['tx']))  
{
    $payment_status = $_GET['st'];
    $transaction_id = $_GET['tx'];

    if($payment_status=='Completed')
    {
       //further coding
    }
}

但是，当我从商家付款到个人/买家帐户时，我没有获得paypal参数作为回报。