php 正則獲取優酷id

/**
 * 通過http://player.youku.com/player.php/sid/XMjUyMjAwMTAyMA==/v.swf
 * 獲取優酷id（XMjUyMjAwMTAyMA）
 *
 * http://player.youku.com/player.php/sid/XMjUyMjAwMTAyMA==/v.swf  =>  XMjUyMjAwMTAyMA
 * @param string $url
 * @return string
 */
function getYouKuIdByYouKuVideoUrl($url = '')
{
    if (empty($url) || (strpos($url, 'http') === false)) return $url;

    preg_match("/sid\/(\w+)/", $url, $new_url);

    if (!empty($new_url)) {
        $video_id = !empty($new_url[1]) ? $new_url[1] : $url;
    } else {
        $video_id = $url;
    }

    return $video_id;
}

$url = 'http://player.youku.com/player.php/sid/XMjUyMjAwMTAyMA==/v.swf';
$video_id = getYouKuIdByYouKuVideoUrl($url);
var_dump($video_id);exit;// XMjUyMjAwMTAyMA