TransactionSearchBasic() amountPaid & amountRemaining Null - php

Question

When i use the following php code with the 2016 Netsuite toolkit to retrieve an invoice, the returned object has the properties amountPaid & amountRemaining but they are both Null. Why are they not showing the values they should be, why include them if only always empty, and whats the best way around this ?
$search = new TransactionSearchBasic();
$SearchLongField = new SearchLongField();
$SearchLongField->searchValue = $internalId;
$SearchLongField->operator = "equalTo";
$search->internalIdNumber = $SearchLongField;
$_csearch = new RecordRef();
$_csearch->type = 'customer';
$_csearch->internalId = $customerId;
$custSearchField = new SearchMultiSelectField();
$custSearchField->searchValue[] = $_csearch;
$custSearchField->operator = "anyOf";
$search->entity = $custSearchField;
$request = new SearchRequest();
$request->searchRecord = $search;
$searchResponse = $this->service->search($request);
$result = json_decode(json_encode($searchResponse), true);
// Return results
return $result;

Answer 1

So though I have not received any outside responses yet, after further research and experimentation Ive come tho the belief that NS will return a full object structure for each data type whether all the properties (keys) are set or not.
And in the case of TransactionSearchBasic and other SearchBasic extensions it only returns a 'basic' subset of common fields used, the others just have Null as their value.
To get these extra data fields populated you have to request them with TransactionSearchAdvanced, and either a saved search or using the columns field. The flip side of this is as far as i can tell, you have to specify all columns you want, there's no way to just add a few extra fields to a Basic search.
NS API documentation is almost non-existent, but i work off this:
http://www.netsuite.com/help/helpcenter/en_US/srbrowser/Browser2016_2/schema/search/transactionsearchadvanced.html?mode=package
and recently found this:
https://usergroup.netsuite.com/users/