PayPal "Security header is not valid" Fehlermeldung. Was mit diesem zu tun?

Ich bin mit PayPal DoDirectPayment API für die payment-integration. Ich erhalte eine Fehlermeldung wie unten.

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Security error:
Error no: 10002
Error message: Security header is not valid

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Hier ist mein code,

    $environment = 'sandbox';
    //Set up your API credentials, PayPal end point, and API version.
    $API_UserName = urlencode('xxxxxxxx');
    $API_Password = urlencode('xxxxxxxx');
    $API_Signature = urlencode('xxxxxxxxxxxxxxxxxxxxxxxxxxx');
    $API_Endpoint = "https://api-3t.paypal.com/nvp";
    if("sandbox" === $environment || "beta-sandbox" === $environment) {
        $API_Endpoint = "https://api-3t.$environment.paypal.com/nvp";
    }
    $version = urlencode('51.0');

    //setting the curl parameters.
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $API_Endpoint);
    curl_setopt($ch, CURLOPT_VERBOSE, 1);

    //Set the curl parameters.
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);

    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);

    //Set the API operation, version, and API signature in the request.
    $nvpreq = "METHOD=$methodName_&VERSION=$version&PWD=$API_Password&USER=$API_UserName&SIGNATURE=$API_Signature$nvpStr_";

    //Set the request as a POST FIELD for curl.
    curl_setopt($ch, CURLOPT_POSTFIELDS, $nvpreq);

    //Get response from the server.
    $httpResponse = curl_exec($ch);

Bitte helfen Sie mir aus diesem problem.

Dank.

InformationsquelleAutor gautamlakum | 2010-10-11