The problem is, that there is no standard way of making asynchronous function or other calls in PHP version 5.
In search for async calls I found, that socket version works for me. Here is link to example from W-Shadow.com: How To Run A PHP Script In The Background
When you call Windows API function SetFileAttributes, it ignores FILE_ATTRIBUTE_COMPRESSED (0x800) and FILE_ATTRIBUTE_ENCRYPTED (0x4000) values passed as parameters.
Most likely it is implemented in this way, because you can pass value from GetFileAttributes, FindFirstFile and FindNextFile without modifications to SetFileAttributes.
This applies to Windows XP, Windows Server 2003 / 2008, Windows Vista.