zcrmsdk/oauth/exception/ZohoOAuthException with message 'Refresh token is not provided.'

Hi Team,

I'm currently following this code sample: https://www.zoho.com/crm/developer/docs/php-sdk/module-sample.html?src=field_details

In my $configuration array I have set:-

$configuration['client_id'] = {client_id};
$configuration['client_secret'] = {client_secret};
$configuration['redirect_uri'] = {redirect_uri};
$configuration['currentUserEmail'] = {currentUserEmail};
$configuration['apiVersion'] = "v2";
$configuration['sandbox'] = true;
$configuration['applicationLogFilePath'] = {applicationLogFilePath};
$configuration['db_port'] = {db_port};
$configuration['db_username'] = {db_username};
$configuration['db_password'] = {db_password};
$configuration['token_persistence_path'] = ""; //had to set empty string due to SDK bug

The module I'm trying to access is "Leads" and the field I'm trying to get details from is "Lead_Status"

However an error is thrown when I read this line: '$response = $moduleIns->getFieldDetails("Lead_Status");'

The error is: 'zcrmsdk/oauth/exception/ZohoOAuthException with message 'Refresh token is not provided.''

There is no accompanying stack trace.

It's my understanding that the PHP SDK is supposed to handle token persistence. However is does not appear to be doing so.

To kick start the process I have manually inserted a manually generated access and refresh tocken into the database however this has had no affect. In fact I can't see the SDK attempting to access the database at all.

Is this a bug? How do I fix this? Why isn't there any documentation for the PHP SDK?