Description:
------------
I noticed a behavior with PHP 5.2.x that I found disturbing.  PHP is matching variables initialized to zero, an empty array and false with NULL.  From the documentation here:

http://us2.php.net/NULL

The only thing that should match NULL are ones that meet these criteria:

A variable is considered to be null if: 

 - it has been assigned the constant NULL. 
 - it has not been set to any value yet. 
 - it has been unset(). 

The function empty() should return true in the above cases (and does), but a comparison operator of == should not.  FYI, is_null() returns false and the === operator works as expected too.


Reproduce code:
---------------
<?php
  $empty_array = array();
  if ($empty_array == NULL)
    echo "Empty array, same as NULL\n";
  else
    echo "Empty array, diff from NULL\n";

  $zero = 0;
  if ($zero == NULL)
    echo "Zero, same as NULL\n";
  else
    echo "Zero, different from NULL\n";
?>

Expected result:
----------------
Empty array, diff from NULL
Zero, different from NULL

Actual result:
--------------
Empty array, same as NULL
Zero, same as NULL