Description:
------------
On Mac OS X, when fopen() fails with a permission denied 
error, the result of a subsequent posix_get_last_error() 
call is zero (0).  I would expect this to be set to the 
value of errno returned by the underlying open or fopen 
call.

I would also expect this to work for put_file_contents, but 
also get a rather useless zero when calling 
posix_get_last_error() after that fails.  However, since 
that isn't a POSIX function, I can accept that it wouldn't 
behave in this way... but fopen is a standard POSIX 
function, and should be setting errno.

Currently, it appears that without explicitly doing a stat 
on the directory, it is impossible to distinguish a 
permissions problem from some other error return (e.g. file 
exists, I/O error, etc.).


Reproduce code:
---------------
$fp = fopen("/unwritabledirectory/filename", "w");
if (!$fp) {
print "Error was: ".posix_get_last_error().".\n";
}


Expected result:
----------------
I would expect the fopen to fail with a permission denied 
error, errno to be set appropriately, and posix_get_last_error
() to fetch that value.


Actual result:
--------------
Error is always zero (0).