PayPal”；授权失败”；

（这是我第一次使用PayPal API，请耐心等待。）

我正在尝试使用BMCreateButton API动态创建加密按钮，使用此页面中经过轻微修改的代码。不幸的是，我似乎无法做到这一点，因为我在PHP错误日志中收到了一条"身份验证/授权失败"的消息。（我也在PayPal开发者论坛上问过这个问题，但没有得到答案。）

此代码：

function createButton($name, $price) {
    // Check to make sure that our version of PHP supports SOAP.
    if((PHP_VERSION_ID < 50101) || !in_array("soap", get_loaded_extensions())) {
        error_log("PHP not running with SOAP");
    } else {
        include_once("config.php"); //this file holds the credentials and whether it's running in sandbox mode or not
        //basic variable validation
        $price = floatval($price);
        // Import the PayPal WSDL.
        $location = $sandbox ? "https://api-3t.sandbox.paypal.com/2.0/" : "https://api-3t.paypal.com/2.0/";
        $soapClient = new SoapClient("https://www.paypalobjects.com/wsdl/PayPalSvc.wsdl", array(
            location => $location
        ));
        // Set our API credentials.
        $credentials->Credentials->Username = $username;
        $credentials->Credentials->Password = $password;
        $credentials->Credentials->Signature = $signature;
        $soapClient->__setSoapHeaders(new SoapHeader("urn:ebay:api:PayPalAPI", "RequesterCredentials", $credentials));
        // Start creating our BMCreateButtonReq object.  For full details about this object, see
        // http://tinyurl.com/3mxau6j .
        $BMCreateButtonReq->BMCreateButtonRequest->Version = "71.0";
        $BMCreateButtonReq->BMCreateButtonRequest->ButtonCode = "ENCRYPTED";
        // What type of button are we creating?
        $BMCreateButtonReq->BMCreateButtonRequest->ButtonType = "CART";
        // Specific variables for this button.  For the full list of options, see
        // http://tinyurl.com/6qyanl .  For a basic payment, these two should be enough.
        $BMCreateButtonReq->BMCreateButtonRequest->ButtonVar[] = "amount=$price";
        $BMCreateButtonReq->BMCreateButtonRequest->ButtonVar[] = "item_name=$name";
        // Run the API call.
        $response = $soapClient->BMCreateButton($BMCreateButtonReq);
        if($response->Ack == "Success" || $response->Ack == "SuccessWithWarning") {
            // If successful, the button code will be in the Website element of $response.
            // It'll be a full HTML form, so don't wrap it in any <form> tags -- just
            // display it as-is.
            echo $response->Website;
        } else {
            error_log("Could not create PayPal button. " . serialize($response->Errors));
            echo "<p class='"note'">Cannot create button</p>";
        }
    }
}

在错误日志中给出：

Could not create PayPal button. O:8:"stdClass":4:{s:12:"ShortMessage";s:35:"Authentication/Authorization Failed";s:11:"LongMessage";s:49:"You do not have permissions to make this API call";s:9:"ErrorCode";s:5:"10002";s:12:"SeverityCode";s:5:"Error";}

我已经检查了凭据，它们是正确的，沙箱和API都失败了。我是否遗漏了一些基本的东西，或者代码中是否存在我可能忽略的错误？