ext/json/tests/003.php is not really the problem. It just uses circular data structure and leaks are expected. 

The real problem that the following code creates broken circular data structure. It shouldn't create circular data ctructure at all.

Reproduce code:
---------------
<?php
$a = array();
$a[] = $a;
var_dump($a);
?>

Expected result:
----------------
array(1) {
  [0]=>
  array(0) {
  }
}

Actual result:
--------------
array(1) {
  [0]=>
  array(1) {
    [0]=>
    *RECURSION*
  }
}
[Wed Sep 13 17:31:32 2006]  Script:  '-'
/home/dmitry/php/php5.2/Zend/zend_execute.c(838) :  Freeing 0xB7F4FFF0 (16 bytes), script=-
[Wed Sep 13 17:31:32 2006]  Script:  '-'
/home/dmitry/php/php5.2/Zend/zend_vm_execute.h(18054) :  Freeing 0xB7F50A60 (44 bytes), script=-
/home/dmitry/php/php5.2/Zend/zend_API.c(819) : Actual location (location was relayed)
Last leak repeated 1 time
[Wed Sep 13 17:31:32 2006]  Script:  '-'
/home/dmitry/php/php5.2/Zend/zend_execute.c(1079) :  Freeing 0xB7F50AF4 (35 bytes), script=-
/home/dmitry/php/php5.2/Zend/zend_hash.c(383) : Actual location (location was relayed)
=== Total 4 memory leaks detected ===

The reason of this bug is IS_CV variables that changed default order of operand fetches.

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.