public function exportFieldNames($format = 'php', $field = null)
    {
        $data = array(
                'token' => $this->apiToken,
                'content' => 'exportFieldNames',
                'returnFormat' => 'json'
        );
        
        #---------------------------------------
        # Process arguments
        #---------------------------------------
        $legalFormats = array('csv', 'json', 'php', 'xml');
        $data['format'] = $this->processFormatArgument($format, $legalFormats);
        $data['field']  = $this->processFieldArgument($field, $required = false);
        
        $fieldNames = $this->connection->callWithArray($data);
        $fieldNames = $this->processExportResult($fieldNames, $format);
        
        return $fieldNames;
    }