maciej@debian:~$ php -v
PHP 5.3.3-7+squeeze3 with Suhosin-Patch (cli) (built: Jun 28 2011 08:24:40)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
    with Xdebug v2.1.0, Copyright (c) 2002-2010, by Derick Rethans
    with Suhosin v0.9.32.1, Copyright (c) 2007-2010, by SektionEins GmbH

maciej@debian:~$ php -r 'namespace foo; const bar = 123;  namespace boo; const bar = 234; echo \foo\bar . PHP_EOL; echo \boo\bar . PHP_EOL;'
123
234