Braintree Drop-In (cards & paypal) + subscriptions (PHP). Problem with paymentMethodNonce - php

Question

I have been able to create a test check-out (js+php) in my server using the Braintree drop-in method. I need to create subscriptions for my customers accepting paypal or credit cards. The checkout (client-side) form is working and I POST it to a php page where I get the form data and create the Customer, plan, etc.
However, I have problems when creating the subscription. I get the Cannot use a paymentMethodNonce more than once or similar errors.
This is what I do:
checkout form (drop-in) submits data to subscription.php?payload_nonce=tokencc_bc_s27k55_c7pcq8_8mvd43_xxcvvf_9p5
braintree.dropin.create({
authorization: 'sandbox_6vqkmmsy_fs5432wttyb8qpzf',
container: '#dropin-container',
locale: 'es_ES',
paypal: {
flow: 'vault'
}
}, function (createErr, instance) {
button.addEventListener('click', function () {
instance.requestPaymentMethod(function (err, payload) {
// Submit payload.nonce to your server
url = 'subscription.html?payload_nonce=' + payload.nonce;
window.location.replace(url);
});
});
});
Then in the destination page I create the Customer...
$payload_nonce = $_GET['payload_nonce'];
$result = Braintree_Customer::create(array(
'firstName' => $name,
'email' => $email,
'company' => $company
));
...his payment method...
$resultPM = Braintree_PaymentMethod::create([
'customerId' => $customerId,
'paymentMethodNonce' => $payload_nonce
]);
...and finally the subscription...
$subscriptionData = array(
'paymentMethodNonce' => $payload_nonce,
'planId' => $billingplan
);
$result = Braintree_Subscription::create($subscriptionData);
I have tried to add the paymentMethodNonce when creating the Customer, or when creating the paymentMethod, etc. with same results.
If the payment method is "credit card" I can get the mayment method token like this:
'paymentMethodToken' => $result->customer->creditCards[0]->token
But if it is PayPal there is no creditcards[0]. Which is the correct method to achieve what I need?
Thanks!