public function get_archive_years($options = array())
{
    $options = array_merge(
        array('post_type' => 'xxx', 'type' => 'yearly', 'after' => "<format>%s,</format>", 'echo' => 0),
        $options
    );
    $tmp = wp_get_archives($options);
    $tmp = explode(",", $tmp);
    array_pop($tmp);
    return $tmp;
}