Description:
------------
Searching for the behavior of all file functions and the right locking mechanisms I tried to use fopen(filename,xb) with former umask(0222). That was intended to trigger an error and look into $php_errormsg

But $php_errormsg was disappeared

Reproduce code:
---------------
error_reporting(E_ALL);
ini_set('track_errors','1');
$dateiname = 'opentest123.txt';
$mask = umask(0222);
echo "<br />Mask: $mask<br />";
$fh = fopen($dateiname,'xb+');
$_errors = debug_backtrace();
if (!$fh)
{
  echo "<br />Fehler: $php_errormsg<br />";
  echo "<br />Fehler: $php_errormsg<br />";
  echo '<pre>';
  print_r($_errors);
  echo '</pre>';
}
else
{
  echo "<br />Datei $dateiname wurde angelegt<br />";
  $write_ok = fwrite($fh, 'Testtext');
  echo "<br />Schreibversuch in $dateiname: $php_errormsg<br />";
}


Expected result:
----------------
Fehler: failed to open stream: Permission denied

Actual result:
--------------
Notice: Undefined variable: php_errormsg in /home/thomas/public_html/test/artikel_locking/opentest.php on line 27 

== echo "<br />Schreibversuch in $dateiname: $php_errormsg<br />";