$service = new NetSuiteService();
$search = new TransactionSearchAdvanced();
$internalId = '123';//transaction internalId

$search->criteria->basic->internalIdNumber->searchValue = $internalId;
$search->criteria->basic->internalIdNumber->operator = "equalTo";

$field = new SearchColumnSelectCustomField();
$field->scriptId = 'custbody_os_freight_company';//this is specific to you & found in netsuite
$search->columns->basic->customFieldList->customField[] = $field;

$field = new SearchColumnStringCustomField();
$field->scriptId = 'custbody_os_warehouse_instructions';//this is specific to you & found in netsuite
$search->columns->basic->customFieldList->customField[] = $field;

//and so on, you can keep adding to the customField array the custom fields you want

$request = new SearchRequest();

$request->searchRecord = $search;

$searchResponse = $service->search($request);

$service = new NetSuiteService();
$search = new TransactionSearchAdvanced();
$internalId = '123';//transaction internalId

$search->criteria->basic->internalIdNumber->searchValue = $internalId;
$search->criteria->basic->internalIdNumber->operator = "equalTo";

$CustomSearchRowBasic = new CustomSearchRowBasic();
$CustomSearchRowBasic->customizationRef->scriptId = 'custbody_os_entered_by';//this is specific to you & found in netsuite
$CustomSearchRowBasic->searchRowBasic = new EmployeeSearchRowBasic();
$CustomSearchRowBasic->searchRowBasic->entityId = new SearchColumnStringField();

$search->columns->customSearchJoin[] = $CustomSearchRowBasic;
//and so on, you can keep adding to the customSearchJoin array the custom fields you want         

$request = new SearchRequest();

$request->searchRecord = $search;

$searchResponse = $service->search($request);