不支持的操作数类型 错误.付款后PayPal退货时

我收到错误第 27 行的/home4/moses/public_html/mywebsite.com/ipn-page-template.php 中不支持的操作数类型。

我的所有代码都在 ipn 页面上。

$url = 'https://www.sandbox.paypal.com/cgi-bin/webscr';
// Set up request to PayPal
$request = curl_init();
curl_setopt_array($request, array
(
    CURLOPT_URL => $url,
    CURLOPT_POST => TRUE,
    CURLOPT_POSTFIELDS => http_build_query(array('cmd' => '_notify-validate') + $ipn_post_data),
    CURLOPT_RETURNTRANSFER => TRUE,
    CURLOPT_HEADER => FALSE,
    CURLOPT_SSL_VERIFYPEER => TRUE,
    CURLOPT_CAINFO => 'cacert.pem',
));
// Execute request and get response and status code
$response = curl_exec($request);
$status   = curl_getinfo($request, CURLINFO_HTTP_CODE);
// Close connection
curl_close($request);
if($status == 200 && $response == 'VERIFIED')
{
    $subject = "valid";
    $message = "good";
}
else
{
    $subject = "invalid";
    $message = "bad";
}