Documentation missing: $_SERVER['HTTP_AUTHORIZATION']

Dear Sir/Madam, On the documentation about basic authentication techniques (url: http://www.php.net/manual/en/features.http-auth.php) there is reference to the index "HTTP_AUTHORIZATION" of the $_SERVER super global variable. This is in a sub-note for users of the IIS-ISAPI version of PHP (I'm using v5). HTTP_AUTHORIZATION does not appear to be documented. Can you please explain what this field does? Also, can you confirm that as of php v5, the PHP_AUTH_USER and PHP_AUTH_PW indexes to the $_SERVER super variable do not work under IIS, as is documented in the same page? If this has changed then please tell me. Many Thanks in advance, Andre Sihera.