From a31c6cbab0da52d589794c1edff062e7ddf3306a Mon Sep 17 00:00:00 2001
From: Damien Seguy <dams@php.net>
Date: Mon, 21 May 2001 11:13:29 +0000
Subject: [PATCH] Adding zak's note

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@48031 c90b9560-bf6c-de11-be94-00142212c4b1
---
 functions/var.xml | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/functions/var.xml b/functions/var.xml
index aacdc93a5c..47354531c4 100644
--- a/functions/var.xml
+++ b/functions/var.xml
@@ -810,13 +810,18 @@ show_var($proteins)
     </simpara>
     <para>
      If a variable has been unset with <function>unset</function>,
-     it will no longer be <function>isset</function>.
+     it will no longer be <function>isset</function>. <function>isset</function>
+     will return <literal>FALSE</literal> if testing a variable that has been 
+     set to <literal>NULL</literal>. Also note that a null byte (<literal>"\0"</literal>)
+     is not equivalent to the PHP <literal>NULL</literal> constant. 
      <informalexample>
       <programlisting role="php">
 $a = "test";
-echo isset ($a); // true
+echo isset ($a); // TRUE
 unset ($a);
-echo isset ($a); // false
+echo isset ($a); // FALSE
+$foo = NULL; 
+print isset ($foo); // FALSE 
       </programlisting>
      </informalexample>
     </para>