Issue with Authenticating OCI REST API calls.

Summary:

We're using PHP to call the Oracle cloud REST APIs for some DNS configuration. However, the code we are trying to use is only getting back 401 Authentication Errors.

Content (required):

What we know so far:

1. Direct CLI works. So, the user config information we are trying to reuse in code is correct.
2. Also tried creating new keypairs and using them in code to sign the request.
3. System clock is only varying by approx 1 min, so that isn't the problem.

Have also tried a bunch of changes within the code like lowercase signing url, url encoding it, without host in it, trying single quote '\n' etc. All of them are returning a 401. I'm sure it's something simple that's missing here, so any help from experts here would be awesome!