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Bug #78475 Unsetting or assigning a value to $GLOBALS makes it stop working
Submitted: 2019-08-29 18:14 UTC Modified: 2021-04-14 10:08 UTC
From: ayg at aryeh dot name Assigned: nikic (profile)
Status: Closed Package: Scripting Engine problem
PHP Version: 7.3.9 OS:
Private report: No CVE-ID: None
 [2019-08-29 18:14 UTC] ayg at aryeh dot name
$GLOBALS contains a reference to a magical array that has all the globals in it. Unsetting or assigning a value to it seems to forevermore lose the reference to this magical array, making $GLOBALS a regular old variable that has no connection to defined globals (although it's still a superglobal).

Unsetting or assigning to $GLOBALS probably should fail, just like $this does. I spent some time today trying to debug a scenario where $GLOBALS['someVar'] did not equal $someVar after I had written "global $someVar". It turned out to be because someone had unset $GLOBALS somewhere (they were trying to clear all global variables and restore them to an earlier state). This is really confusing and should be disallowed. Or at least produce a notice or something.

Test script:
$a = 1;
unset( $GLOBALS );
function f() {
  global $a;
  unset( $GLOBALS ); // $GLOBALS = []; is the same
  var_dump( $a );
  var_dump( isset( $GLOBALS['a' ) );

Expected result:




Actual result:


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 [2021-04-14 10:08 UTC]
-Status: Open +Status: Closed -Assigned To: +Assigned To: nikic
 [2021-04-14 10:08 UTC]
unset($GLOBALS) results in a compile-time error in PHP 8.1, as part of
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