Method external_idHeader

public function external_idHeader(&$options)
{
    $data = array('class' => 'ph-upc', 'title' => 'COM_PHOCACART_FIELD_EXTERNAL_PRODUCT_ID_LABEL', 'tool' => 'searchtools.sort', 'column' => 'a.external_id');
    return $this->renderHeaderColumn($data, $options);
}