Save credit card into Paypal - php

Question

I am trying to save credit card into paypal using paypal php sdk using the bellow code.
<?php
require 'PayPal-PHP-SDK-master/vendor/autoload.php';
$clientId = 'XXXXXXXXXX';
$clientSecret = 'XXXXXXXXX';
use PayPal\Auth\OAuthTokenCredential;
use PayPal\Api\CreditCard;
use PayPal\Rest\ApiContext;
$sdkConfig = array(
"mode" => "sandbox"
);
$apiContext = $apiContext = new ApiContext(new OAuthTokenCredential(
$clientId,
$clientSecret
));
$creditcard = new CreditCard();
$creditcard->setId(101);
$creditcard->setNumber('4111111111111111');
$creditcard->setType('visa');
$creditcard->setExpireMonth(12);
$creditcard->setExpireYear(2020);
$creditcard->setCvv2(123);
$request = clone $creditcard;
try {
$output = $creditcard->create($apiContext);
echo "success";
} catch (Exception $ex) {
echo $ex;
exit(1);
}
But it is not working and i got exception like bellow
exception 'PayPal\Exception\PayPalConnectionException' with message
'Got Http response code 400 when accessing
https://api.sandbox.paypal.com/v1/vault/credit-cards.' in
/var/www/html/test/paypalcard/PayPal-PHP-SDK-master/lib/PayPal/Core/PayPalHttpConnection.php:202
Stack trace: #0
/var/www/html/test/paypalcard/PayPal-PHP-SDK-master/lib/PayPal/Transport/PayPalRestCall.php(78):
PayPal\Core\PayPalHttpConnection->execute('{"id":101,"numb...') #1
/var/www/html/test/paypalcard/PayPal-PHP-SDK-master/lib/PayPal/Common/PayPalResourceModel.php(104):
PayPal\Transport\PayPalRestCall->execute(Array, '/v1/vault/credi...',
'POST', '{"id":101,"numb...', NULL) #2
/var/www/html/test/paypalcard/PayPal-PHP-SDK-master/lib/PayPal/Api/CreditCard.php(443):
PayPal\Common\PayPalResourceModel::executeCall('/v1/vault/credi...',
'POST', '{"id":101,"numb...', NULL, Object(PayPal\Rest\ApiContext),
NULL) #3 /var/www/html/test/paypalcard/cardtest.php(32):
PayPal\Api\CreditCard->create(Object(PayPal\Rest\ApiContext)) #4
{main}
What is wrong with my code and what changes need to add for this?