问表达式引擎save_entry()函数的参数中的'field_ft_‘是什么

EN

ee()->load->library('api');
ee()->api->instantiate('channel_entries');
ee()->api->instantiate('channel_fields');

$data = array(
    'title'         => 'Breaking News Story!',
    'entry_date'    => '1256953732',
    'edit_date'     => '1351653729',
    'field_id_6'    => 'Some data',
    'field_ft_6'    => 'none',
    'field_id_19'   => 'More data',
    'field_ft_19'   => 'xhtml'
);

ee()->api_channel_fields->setup_entry_settings($channel_id, $data);

$success = ee()->api_channel_entries->save_entry($data, $channel_id);

    if ( ! $success)
    {
            show_error(implode('<br />', $this->api_channel_entries->errors));
    }