UtfSafeString::getLastPosition

static function getLastPosition($haystack, $needle)
{
	if (Application::isUtfMode())
	{
		//mb_strrpos does not work on invalid UTF-8 strings
		$ln = mb_strlen($needle);
		for ($i = mb_strlen($haystack) - $ln; $i >= 0; $i--)
		{
			if (mb_substr($haystack, $i, $ln) == $needle)
			{
				return $i;
			}
		}
		return false;
	}

	return mb_strrpos($haystack, $needle);
}