new SoapClient() with connection_timeout = NULL breaks multi-dimensional arrays

EXAMPLE CODE:
<?php

$header = array();
$header["header_general"]["order_type"] = "SHOP";
print_r( $header );

#$timeout = 1;
$client = new SoapClient( null, array( 'location' => 'www.silversolutions.de', 'uri' => 'www.silversolutions.de', 'connection_timeout' => $timeout ) );

$header = array();
$header["header_general"]["order_type"] = "SHOP";
print_r( $header );

?>

COMMAND:
php -n test.php
(NO CONFIG IS USED!!)

ACTUAL OUTPUT:
Array
(
    [header_general] => Array
        (
            [order_type] => SHOP
        )

)

Warning: Cannot use a scalar value as an array in /home/mab/test.php on line 11
Array
(
    [header_general] => 0
)

EXPECTED OUTPUT:
Array
(
    [header_general] => Array
        (
            [order_type] => SHOP
        )

)

Warning: Cannot use a scalar value as an array in /home/mab/test.php on line 11
Array
(
    [header_general] => Array
        (
            [order_type] => SHOP
        )

)

This is on
Linux johndoe 3.2.0-24-virtual #37-Ubuntu SMP Wed Apr 25 10:17:19 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux.

On a desktop machine with
Linux johndoe 3.2.0-24-generic #38-Ubuntu SMP Tue May 1 16:18:50 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
it works as expected.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: php5 5.3.10-1ubuntu3.1
ProcVersionSignature: Ubuntu 3.2.0-24.37-virtual 3.2.14
Uname: Linux 3.2.0-24-virtual x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Tue May 15 12:55:50 2012
PackageArchitecture: all
SourcePackage: php5
UpgradeStatus: No upgrade log present (probably fresh install)