Description:
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Defining a namespace who's name starts with a \ is interpreted as a constant though resolving a constant for the namespace name is not supported (and should not! :) ) and results in an empty string being used.


Test script:
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test.php:

<?php
 define('a','\foo');
 require 'a.php';


a.php:

<?php
namespace \a; 
var_dump(__NAMESPACE__);
class b { }

Expected result:
----------------
(Parse?) Error due to invalid namespace definition

Actual result:
--------------
Empty string for __NAMESPACE__ or undefined constant a depending wheter or not the file "a.php" got required or called directly