Description:
------------
I found the problem when calling is_writable() after stream_wrapper_register().

It is OK with non-root user, but the result is not as expected with root user.

I want to remain the same permission as no stream_wrapper so I return just what "stat()" returns in "url_stat()" with my stream_wrapper class.

However, in the filestat.c source code, it does special check to root user( getuid() == 0) only with php_plain_files_wrapper. So I got false while calling is_writable after stream_wrapper_register().

I wonder if it is possible to add a function "is_super_user" in the stream_wrapper, and call it while calling permission check functions such as is_readable, is_writable and is_executable in case to keep consistent with system root user where needed.


Test script:
---------------
class TestStream{
        public static function wrap() { stream_wrapper_unregister('file'); stream_wrapper_register('file', get_called_class()); }
        public static function unwrap(){ stream_wrapper_restore('file'); }
        public function url_stat($path, $flags){
                $this->unwrap(); $result = stat($path); $this->wrap();
                return $result;
        }
}
$file = __DIR__."/tmp"; @mkdir($file, 0777, true); chmod($file, 0);
clearstatcache(); var_dump(is_writable($file));
clearstatcache(); TestStream::wrap(); var_dump(is_writable($file)); TestStream::unwrap();
chmod($file, 0777); rmdir($file);

Expected result:
----------------
bool(true)
bool(true)

Actual result:
--------------
bool(true)
bool(false)