Description:
------------
Since upgrading to php: 
 
PHP 4.3.3RC3 (cli) (built: Aug 16 2003 11:22:58) 
Copyright (c) 1997-2003 The PHP Group 
Zend Engine v1.3.0, Copyright (c) 1998-2003 Zend 
Technologies 
 
it seems that many of my php programs which use ! 
is_null($var) have broken, however when I replace the 
function is_null for a comparison: $var != NULL, it works. 
Is this a bug? Or some new "feature"? 
 
Many thanks 

Reproduce code:
---------------
Fails:

        function name ($setTo=NULL)
        {
                if (! is_null($setTo))
                {
			return "Not null";
                }

                return "null";
        }

Works:

        function name ($setTo=NULL)
        {
                if ($setTo != NULL)
                {
			return "Not null";
                }

                return "null";
        }

Expected result:
----------------
return null when null and not null when not null 

Actual result:
--------------
works only with comparison != and not with !is_null() 
function