While handling of global variables had the focus on to be easy in
    PHP 3 and early versions of PHP 4, the focus has changed to be more
    secure. While in PHP 3 the following example worked fine, in PHP 4 it
    has to be unset(unset($GLOBALS["id"]));. This is 
    only one issue of global
    variable handling. You should always have used $GLOBALS, with
    newer versions of PHP 4 you are forced to do so in most cases.
    Read more on this subject in the 
    global references section.
   
Example C-1. Migration of global variables 
<?php $id = 1; function test() {     global $id;     unset($id); } test(); echo($id); // This will print out 1 in PHP 4 ?>
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