PayPal不断得到无效的 ipn

这是我的IPN处理程序：

<?php
include 'constants.php';
include 'classes/class.database.php';
$raw_post_data = file_get_contents('php://input');
$raw_post_array = explode('&', $raw_post_data);
$myPost = array();
foreach ($raw_post_array as $keyval) {
    $keyval = explode ('=', $keyval);
    if (count($keyval) == 2)
        $myPost[$keyval[0]] = urldecode($keyval[1]);
}
$req = 'cmd=_notify-validate';
if(function_exists('get_magic_quotes_gpc')) {
    $get_magic_quotes_exists = true;
}
foreach ($myPost as $key => $value) {
    if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) {
        $value = urlencode(stripslashes($value));
    } else {
        $value = urlencode($value);
    }
    $req .= "&$key=$value";
}
if(USE_SANDBOX == true) {
    $paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr";
} else {
    $paypal_url = "https://www.paypal.com/cgi-bin/webscr";
}
$ch = curl_init($paypal_url);
if ($ch == FALSE) {
    return FALSE;
}
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
if(DEBUG == true) {
    curl_setopt($ch, CURLOPT_HEADER, 1);
    curl_setopt($ch, CURLINFO_HEADER_OUT, 1);
}
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
$res = curl_exec($ch);
if (curl_errno($ch) != 0) // cURL error
    {
    if(DEBUG == true) { 
        error_log(date('[Y-m-d H:i e] '). "Can't connect to PayPal to validate IPN message: " . curl_error($ch) . PHP_EOL, 3, LOG_FILE);
    }
    curl_close($ch);
    exit;
} else {
    if(DEBUG == true) {
        error_log(date('[Y-m-d H:i e] '). "HTTP request of validation request:". curl_getinfo($ch, CURLINFO_HEADER_OUT) ." for IPN payload: $req" . PHP_EOL, 3, LOG_FILE);
        error_log(date('[Y-m-d H:i e] '). "HTTP response of validation request: $res" . PHP_EOL, 3, LOG_FILE);
    }
    curl_close($ch);
}
$tokens = explode("'r'n'r'n", trim($res));
$res = trim(end($tokens));
if (strcmp ($res, "VERIFIED") == 0) {
    $status = $_POST['payment_status'];
    $currency = $_POST['mc_currency'];
    $receiver = $_POST['receiver_email'];
    $buyer = $_POST['payer_email'];
    $buyer_name = $_POST['custom'];
    $db = new Database($sql_host, $sql_user, $sql_pass, $sql_data, "payments");
    $db->connect();
    for ($i = 0; $i < 10; $i++) {
        if (isset($_POST['item_name'.$i])) {
            $db->addPayment($_POST['item_name'.$i], $_POST['item_number'.$i], $status, $_POST['mc_gross_'.$i], $currency, $buyer, $receiver, $buyer_name);
        }
    }
    if(DEBUG == true)
        error_log(date('[Y-m-d H:i e] '). "Verified IPN: $req ". PHP_EOL, 3, LOG_FILE);
} else if (strcmp ($res, "INVALID") == 0) {
    if(DEBUG == true) {
        error_log(date('[Y-m-d H:i e] '). "Invalid IPN: $req" . PHP_EOL, 3, LOG_FILE);
    }
}?>

以下是 IPN 的回报：

无效
[2016-02-28 05：55 UTC]无效的 IPN：cmd=_notify-验证&mc_gross=0.01&protection_eligibility=合格&address_status=已确认&item_number1=36&payer_id=7GXJG3SBPYHEY&tax=0.00&address_street=&payment_date=21%3A55%3A22+Feb+27%2C+2016+PST&payment_status=已完成&字符集=UTF-8&address_zip=&mc_shipping=0.00&mc_handling=0.00&first_name=&mc_fee=0.01&address_country_code=GB&address_name=&notify_version=3.8&custom=Alex&payer_status=verified&business=&address_country=United+Kingdom&num_cart_items=1&mc_handling1=0.00&address_city=&verify_sign=AzEkqtmA1WmF4x7TDnCOWp34hPjAASvAQSuGR4.BNB0U46x2nInwBmEo&payer_email=&mc_shipping1=0.00&tax1=0.00&txn_id=50446034DM994872C&payment_type=即时&payer_business_name=&last_name=&address_state=&item_name1=测试+%28DO+not+buy%29&receiver_email=***&payment_fee=0.01&数量1=1&receiver_id=RJ5DJ76VDC7RC&txn_type=购物车&mc_gross_1=0.01&mc_currency=美元&residence_country=GB&transaction_subject=&payment_gross=0.01&ipn_track_id=487a9f43c92

任何帮助都会很棒。