I was getting some error In a larger script I wrote which worked fine with php3..x.  For some reason thou I came to find out that $null or $NULL was equal to 0 for some reason.  I dont know if this was intended or not but if it wasn't that seems like a bug to me anyways.  Usually null is set to be equal to \0 maybe the \ is missing somewhere or something.  

here is a small script to try to see the results I got.
<?
$test = 0;
if ($test == $NULL)
        print "yes";
else
        print "No";
?>