Error in call to API function "auth/token/from_oauth1": Bad HTTP "Content-Type" header: "application

[Cross-linking for reference: https://stackoverflow.com/questions/50795358/error-in-call-to-api-function-auth-token-from-oauth1-bad-http-content-type ]

The error message is indicating that your client is sending up an unexpected Content-Type value (using a boundary), when it needs to be using one of the listed expected values.

This appears to be happening because you're just sending the POST fields directly. You need to sending JSON though, so you would put your CURLOPT_POSTFIELDS array inside json_encode().

Also, note that this endpoint is only meant for use if you already have pre-existing OAuth 1 access tokens. If you don't have pre-existing OAuth 1 access tokens, you should send the user through the normal OAuth 2 app authorization flow. You can find information on how that works in the OAuth guide here:

https://www.dropbox.com/developers/reference/oauth-guide

The documentation for the OAuth 2 app authorization flow can be found here:

https://www.dropbox.com/developers/documentation/http/documentation#authorization