PHP 获取网页301真实地址

$header = get_headers($url, 1);
if (strpos($header[0], '301') || strpos($header[0], '302')) {
if (is_array($header['Location'])) {
return $header['Location'][count($header['Location'])-1];
} else {
return $header['Location'];
}
} else {
return $url;
}