Description:
------------
MKDIR has a strange behaviour. In my case, I tried to the following:

- Create a directory A
- Change group of A
- Create directory B which is a sub-directory of A -> ERROR

I wrote a test case. 
The strange thing: 
I create directory A by mkdir('A'); and I change it's group by chgrp('A', 'some_user');. fileowner('A'); return as expected '80' which is the user 'www', but filegroup('A') also returns '80', although it should be '1005' (='some_user'). If I now try an 'ls -l' in a shell I get "www:some_user", which indicates that chgrp('A', 'some_user'); was successfull.



Reproduce code:
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function mk_dir($dir, $ch_grp = true) {
  mkdir($dir);
  if (!is_dir($dir)) {
	echo 'FAIL';
  } else {
	chmod($dir, 504);
	if ($ch_grp) chgrp($dir, 'some_user');
	echo 'SUCCESS';
	echo ', ' . fileperms($dir);
	echo ', ' . fileowner($dir);
	echo ', ' . filegroup($dir);
  }
}


mk_dir('/var/www/directory/test1');
	// OUTPUT: SUCCESS, 16877, 80, 80
mk_dir('/var/www/directory/test1/test2');
	// OUTPUT: FAIL, 16877, 80, 80
rmdir('/var/www/directory/test1/test2'); // CLEAN UP
rmdir('/var/www/directory/test1');       // CLEAN UP

mk_dir('/var/www/directory/test1', false);
	// OUTPUT: SUCCESS, 16877, 80, 80
mk_dir('/var/www/directory/test1/test2', false);
	// OUTPUT: SUCCESS, 16877, 80, 80
rmdir('/var/www/directory/test1/test2'); // CLEAN UP
rmdir('/var/www/directory/test1');       // CLEAN UP