public static function footer_button($href, $text, $extra = [], $type = 'button')
{
$defaults = ['class' => 'btn btn-default js-' . o::websafe($text), 'href' => $href];
$list = array_merge($defaults, (array) $extra);
echo ' ';
echo o::element_rtn($type, $list, $text);
}
