Php paypal成功url返回空

我有一个简单的paypal结账表，当我用沙盒凭证将它发布到paypal时，当PayDevices成功时，它没有给我交易和货币之类的东西，我确实打印了它，但什么都没有。我正在使用codeigniter

以下是表格代码

<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_click">
<input type="hidden" name="business" value="dev1@ferozitech.com">
<input type="hidden" name="item_name" value="test" class="slug">
<input type="hidden" name="item_number" value="2" class="proposalId">
<input type="hidden" name="custom" value="" class="userId">
<input type="hidden" name="amount" value="40" class="amount">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="return" value="<?php echo base_url('payment/payment_complete/') ?>">
<input type="hidden" name="cancel_return" value="<?php echo base_url('payment/payment_cancel') ?>">
<input type="image" name="submit" src="<?php echo base_url('images/checkoutpaypal.png'); ?>" alt="PayPal - The safer, easier way to pay online">
</form>

尝试以下代码：
通知输入字段在哪里？我刚刚从开发人员那里复制了上面的代码，是否遗漏了什么。？是的，您遗漏了这个
什么是$notify\u url？它是干什么用的？
http://www.codexworld.com/how-to-guides/paypal-ipn-notify-url-not-working-sandbox-account/
这将帮助您，当您想要检查paypal响应时，您必须使用通知url，它将在
$\u POST中为您提供付款状态通知
Try this code:


<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="dev1@ferozitech.com">
<input type="hidden" name="item_name" value="test" class="slug">
<input type="hidden" name="item_number" value="2" class="proposalId">
<input type="hidden" name="custom" value="" class="userId">
<input type="hidden" name="amount" value="40" class="amount">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="rm" value="2" />
<input type="hidden" name="lc" value=""/>
<input type="hidden" name="no_note" value="1"/>
<input type="hidden" name="return" value="<?php echo base_url('payment/payment_complete/') ?>">
<input type="hidden" name="cancel_return" value="<?php echo base_url('payment/payment_cancel') ?>">
<input type="hidden" name="notify_url" value="<?php echo base_url('payment/payment_complete/') ?>" />
<input type="image" name="submit" src="<?php echo base_url('images/checkoutpaypal.png'); ?>" alt="PayPal - The safer, easier way to pay online"> 
</form>

Return url notify_url payment_complete function

print_r($_REQUEST);die;