如何通过PHP代码使用REST API取消Paypal计费协议

$clientId = "YOUR_CLIENT_ID";
$secret = "YOUR_SECRET";

$auth = base64_encode($clientId . ":" . $secret);

$headers = array(
    "Content-Type: application/json",
    "Authorization: Basic " . $auth
);

$agreementId = "YOUR_AGREEMENT_ID";

$data = array(
    "note" => "Canceling the agreement"
);

$jsonData = json_encode($data);

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "https://api.paypal.com/v1/payments/billing-agreements/" . $agreementId . "/cancel");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$response = curl_exec($ch);

curl_close($ch);

$result = json_decode($response, true);

if ($result['state'] == 'Cancelled') {
    echo "The billing agreement has been successfully cancelled.";
} else {
    echo "Failed to cancel the billing agreement.";
}