PHP code to obtain the ID numbers of all child and grandchild columns of a column

/***
 @ Get sub-column ID number
 @ bbs.it-home.org
 @ 2013/2/26
*/
private function sonCategoryIds($categoryID)
{
    //@初始化栏目数组
    $array[] = $categoryID;

    do
    {
        $ids = '';
        $temp = $this->mysql->select('SELECT `id` FROM `pcb_article_category` WHERE `parentID` IN (' . $categoryID . ')');
        foreach ($temp as $v)
        {
            $array[] = $v['id'];
            $ids .= ',' . $v['id'];
        }
        $ids = substr($ids, 1, strlen($ids));
        $categoryID = $ids;
    }
    while (!empty($temp));
    $ids = implode(',', $array);

    return $ids;
}
?>