Path::normalize

static function normalize($path)
{
	if (!is_string($path) || ($path == ""))
		return null;

	//slashes doesn't matter for Windows
	static $pattern = null, $tailPattern;
	if (!$pattern)
	{
		if(strncasecmp(PHP_OS, "WIN", 3) == 0)
		{
			//windows
			$pattern = "'[\\/]+'";
			$tailPattern = ".\/+ ";
		}
		else
		{
			//unix
			$pattern = "'[/]+'";
			$tailPattern = "/";
		}
	}
	$pathTmp = preg_replace($pattern, "/", $path);

	if (strpos($pathTmp, "") !== false)
		throw new InvalidPathException($path);

	if (preg_match("#(^|/)(\.|\.\.)(/|$)#", $pathTmp))
	{
		$arPathTmp = explode('/', $pathTmp);
		$arPathStack = array();
		foreach ($arPathTmp as $i => $pathPart)
		{
			if ($pathPart === '.')
				continue;

			if ($pathPart === "..")
			{
				if (array_pop($arPathStack) === null)
					throw new InvalidPathException($path);
			}
			else
			{
				array_push($arPathStack, $pathPart);
			}
		}
		$pathTmp = implode("/", $arPathStack);
	}

	$pathTmp = rtrim($pathTmp, $tailPattern);

	if (mb_substr($path, 0, 1) === "/" && mb_substr($pathTmp, 0, 1) !== "/")
		$pathTmp = "/".$pathTmp;

	if ($pathTmp === '')
		$pathTmp = "/";

	return $pathTmp;
}