根据子ID获取顶级父级id

/**
 * 根据子ID获取顶级父级id
 *
 * @param [type] $id
 * @return void
 */
function getparentid($id)
{
    $sql = Db::name('category')->field('id,pid')->select();
    $arr = [];
    foreach ($sql as $key => $value) {
        $arr[$value['id']] = $value['pid'];
    }
    while ($arr[$id]) {
        $id = $arr[$id];
    }
    return $id;
}