$session->array['dummy''] = true;
$session->array['testkey'] = 1;

$ php -v
PHP 5.1.6 (cgi-fcgi) (built: Oct 24 2006 19:38:28)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
$ svn update
uname At revision 3015.
$ uname -a
Linux sandbox.zend.com 2.6.9-34.EL #1 Fri Feb 24 16:44:51 EST 2006 i686 i686 i386 GNU/Linux

$ php -v
PHP 5.2.0 (cgi-fcgi) (built: Dec 19 2006 15:37:32)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2006 Zend Technologies

gavin@IBM-F4F0A5528C1 ~/src/zftrunk/tests/Zend/Session
$ uname -a
CYGWIN_NT-5.1 IBM-F4F0A5528C1 1.5.22(0.156/4/2) 2006-11-13 17:01 i686 Cygwin

gavin@IBM-F4F0A5528C1 ~/src/zftrunk/tests/Zend/Session
$ svn update
At revision 3016.

<?php

session_start();

$_SESSION['anArray'] = array('a', 'b', 'c');
echo "\n\$_SESSION = ";
print_r($_SESSION);

class TestSessionRef
{
    public function &__get($name)
    {
        echo "\nReturning \$_SESSION[$name] by reference\n";
        return $_SESSION[$name];
    }
}

$test = new TestSessionRef();
$test->anArray['foo'] = 'bar';
echo "\n\$test->anArray = ";
print_r($test->anArray);

echo "\n\$a = ";
$a = & $test->anArray;
$a['bee'] = 'honey';
print_r($a);

echo "\n\$_SESSION = ";
print_r($_SESSION);

Work-around

Do not modify an array, after assigning it to a session namespace key.

http://bugs.php.net/bug.php?id=36214

The new Zend_Session unit test passes with PHP 5.2.1RC4 (and hopefully will continue to pass with PHP 5.2.1+):
http://bugs.php.net/bug.php?id=39449

If no further problems are found, after PHP 5.2.1 is released, then I will close this issue.

Everyone using an earlier version of PHP should use the workaround above.

Another Work-Around

$myNamespace = new Zend_Session_Namespace('mySpace');

// works, even for broken versions of PHP
$a = array(1,2,3);
$myNamespace->someArray = array( & $a ) ;
$a['foo'] = 'bar';