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Each of your routes (the create route, and the capture route) must return a response that is a JSON string, and no other text nor HTML. print_r is not suitable.

Probably you need to hit a curl request with required attributes.

You can dd() the response of the curl response and surely you ll get the status.

I would assume the reference_id is something we generate ourselves

Yes, that appears to be the case.

If you look under https://developer.paypal.com/docs/api/orders/v2/#definition-purchase_unit, there it says,

reference_id - string - The API caller-provided external ID for the purchase unit.

So you, as the caller of the API, have to provide this ID.

When PayPal processes payments, any information about the funding source -- including the billing address -- is kept private to payers' accounts. This is a reason to prefer using PayPal to make payments on random websites, as that information is kept private by design and cannot be compromised.

Only shipping information (if applicable) is provided in the response.

If you need more billing information from customers, you can collect it yourself. Or if you are a large merchant who habitually collects this information, you can ask PayPal to include it in their API responses and they may consider such a request from a reputable company with established business history, but it will not be there normally.

Payouts run in a batch. For a batch status to begin as 'PENDING' is normal. The status of each payout within the batch is what matters. You can query them as needed, and if they are individually pending some reason may be given.

The most common reason for a PayPal payment to be pending in sandbox or live is if there is no PayPal account with a confirmed email (in sandbox or live, respectively) at the address to which the payment was sent. Receivers have 30 days to create an account and/or confirm the email on their account to accept the payment, otherwise it will be automatically refunded after 30 days. Reminders are sent to that email during this period.

How can I get the failed batch items on order to try again?

If you look at Intuit's documentation, you can see that the HTTP response the API returns contains this information. Here's the example request they show:

Referencing the correct solution so not to misinform! https://stackoverflow.com/a/69004266/1060364

By default, Dropbox API calls operate in the "member folder" ("/Dave Smith" in your example).

You can configure Dropbox API calls to operate in the "team space" instead though, by setting the Dropbox-API-Path-Root header. You can find information on using that in the Team Files Guide.

As explained in comments, you can't change the redirect method back from PayPal. It will always be a GET string appended to your return_url.

However, the ideal and recommended solution is to not use any redirects. At all. Instead, use the PayPal-Checkout-SDK you have to make two routes on your server, one for 'Create Order' and one for 'Capture Order', documented here, that return only JSON data (no HTML or text). The latter one should (on success) store the payment details in your database before it does the return (particularly purchase_units[0].payments.captures[0].id, the PayPal transaction ID)

Pair these two JSON-only routes with the following approval flow that does not use any redirects, and instead keeps your site loaded in the background (lightboxed) at all times during payment approval: https://developer.paypal.com/demo/checkout/#/pattern/server