Paypal обработка платежа

есть форма, как обработать платеж у себя на сайте после оплаты?

<form action="https://www.sandbox.paypal.com/cgi-bin/websc" method="post">
         <input type="hidden" name="cmd" value="_xclick">
         <input type="hidden" name="business" value="mr.dealer-facilitator@mail.ru">
         <input id="paypalItemName" type="hidden" name="item_name" value="5">
         <input id="paypalQuantity" type="hidden" name="quantity" value="1">
         <input id="paypalAmmount" type="hidden" name="amount" value="0.01">
          <input type="hidden" name="return" value="https://jobinchina.co/ipn">
          <input type="hidden" name="custom" value="<?php echo json_encode($customData = ['user_id' => 1, 'product_id' => 1]);?>">
         <input type="hidden" name="currency_code" value="USD">
         <input type="hidden" name="lc" value="US">
         <input type="hidden" name="bn" value="PP-BuyNowBF">
         <button type="submit"> Pay Now</button>
</form>

на странице success выдает false

$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]);
        }
// read the IPN message sent from PayPal and prepend 'cmd=_notify-validate'
        $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";
        }
// Step 2: POST IPN data back to PayPal to validate
        $ch = curl_init('https://ipnpb.paypal.com/cgi-bin/webscr');
        curl_setopt($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);
        curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
// In wamp-like environments that do not come bundled with root authority certificates,
// please download 'cacert.pem' from "https://curl.haxx.se/docs/caextract.html" and set
// the directory path of the certificate as shown below:
// curl_setopt($ch, CURLOPT_CAINFO, dirname(__FILE__) . '/cacert.pem');
        if ( !($res = curl_exec($ch)) ) {
            // error_log("Got " . curl_error($ch) . " when processing IPN data");
            curl_close($ch);
            exit;
        }
        curl_close($ch);
        if (strcmp ($res, "VERIFIED") == 0) {
            return 'true';
        } else if (strcmp ($res, "INVALID") == 0) {
            return 'false';
        }