On 8/27/2013 12:53 PM, Stuart Dallas wrote:
On 27 Aug 2013, at 17:28, Jim Giner <jim.gi...@albanyhandball.com> wrote:

On 8/27/2013 11:56 AM, Stuart Dallas wrote:
Oops, sent this message from the wrong email address, so the list rejected it.

Begin forwarded message:

From: Stuart Dallas <stu...@3ft9.com>
Subject: Re: [PHP] Basic Auth
Date: 27 August 2013 16:36:27 BST
To: jim.gi...@albanyhandball.com
Cc: php-general@lists.php.net

On 27 Aug 2013, at 15:59, Jim Giner <jim.gi...@albanyhandball.com> wrote:

On 8/27/2013 10:55 AM, Stuart Dallas wrote:
On 27 Aug 2013, at 15:51, Jim Giner <jim.gi...@albanyhandball.com> wrote:

On 8/27/2013 10:39 AM, Stuart Dallas wrote:
On 27 Aug 2013, at 15:18, Jim Giner <jim.gi...@albanyhandball.com> wrote:

On 8/27/2013 10:14 AM, Stuart Dallas wrote:
It's not really confusing so long as you understand how PHP works. Each request 
is brand new - nothing is retained from previous requests. The two variable 
you're changing are set by PHP when the request comes in from the browser. The 
fact you changed them in a previous request is irrelevant because 1) that 
change was not communicated to the browser in any way, and 2) PHP doesn't 
retain any data between requests [1].

If you've been coding assuming that changes you make to global variables are 
retained between requests you must have been having some pretty frustrating 


Not really - this is the first time I've had something not work as expected.
That was said with my tongue very much firmly in my cheek, and so is this:

  I've been playing with dynamite since I was 4 - hey, it must be a safe, 
proper thing to do!

Just because nothing has blown up in your face yet doesn't mean it won't, and 
I'm concerned that you might not actually see how important it is to make sure 
you're using the tool correctly.


This may very well be the first time with this problem because I haven't tried 
anything like this before.

That said - can you give me some pointers on how to do the JS solution?  I'm 
calling a script that is similar to the one I used to signon.  It sends out 
something like:

       header("WWW-Authenticate: Basic realm=$realm");
       header('HTTP/1.0 401 Unauthorized');
       echo "<h3>You have entered invalid credentials<br>";
       echo "Click <a href='$return_url'> here </a> to return to the menu.";

when it doesn't detect the PHP_AUTH_USER or it is an invalid value.

So - to effect a signoff, what does one do?   You said to use an invalid value, 
but what do I do with that?  How do I ignore the 401?   Now I'm getting the 
signin dialog and I'm stuck.
You don't need to do anything on the server-side. You simply need a JS function 
that sends a request to a URL that requires basic auth, with an Authenticate 
header that contains an invalid username and password. Then, when your server 
responds with a 401 Authentication required (which it should already do for an 
invalid request) you can set location.href to whatever URL you want the logged 
out user to see.

If you don't know how to make a request from Javascript -- commonly known as an 
AJAX request -- then google for it. I'd recommend the jquery library if you 
want a very easy way to do it.


I am familiar with an ajax request (xmlhttprequest) and I have a function ready to call a 
script to effect this signoff.  I just don't know what to put in that php script I'm calling.  
From what you just wrote I'm guessing that my headers as shown previously  may be close - 
I"m confused about your mention of "contains an invalid username...".  As you 
can see from my sample I don't include such a thing.

 From the Javascript, request any URL that requires authentication - it doesn't 
matter. When you make the AJAX request, pass an Authentication header that 
contains an invalid username and password. If you don't know what I mean by 
that, please google how HTTP Basic Auth works.

It's not the basic auth that I'm having the issue with - it's the 'header' 
thing and understanding what a 401 is doing and how I'm to ignore it.  Never 
had to play with these things before and this part is all new.  Let's face it - 
I'm an applications guy, not a systems guy. All this talk of headers and such 
is greek to me.
HTTP headers are as important for application guys as they are for systems 
guys. I appreciate that this may be new to you, but it's pretty basic knowledge 
about how HTTP works.

Basic auth is simple, and you need to understand how it works to understand 
what I've been trying to say. Here's how HTTP auth works:

1) Browser hits page.
2) The PHP script knows this page requires HTTP Auth, checks the 
PHP_AUTH_[USER|PW] variables but doesn't find anything, so it responds with an 
HTTP status of 401 Unauthorised.
3) The browser gets the 401 response and displays the login box.
4) User enters username and password.
5) Browser sends the request again, but this time with an Authorization header 
containing the username and password. It also caches the username and password 
for use with future requests.
6) PHP populates the PHP_AUTH_[USER|PW] variables with the username and 
password in the Authorization header.
7) The PHP script checks those variables as per step 2, finds them, checks 
they're correct, and then shows the user the page with a 200 OK HTTP response 
(the default with PHP).
8) Every subsequent request the browser sends to that domain will now include 
the Authorization header, so the server will never respond with a 401 status 
again until the browser session ends (i.e. the browser is closed).

So, to log the user out you basically need to override what the browser has 
cached for the username and password. To do this you need to send a request 
with a new username and password (technically just a new username). You can do 
this with a request like http://bogususername:boguspassw...@www.example.com/ 
but the 401 response the server returns will cause the browser to display a 
login box, which is probably not what you want.

So, we do it with Javascript. Send a request using AJAX to any URL that 
requires authentication, setting our own Authorization header with an invalid 
username and password. PHP will see that the username and password are 
incorrect and will respond with a 401 status as per step 2 above, but step 3 
will not happen because AJAX requests don't reach the browser's default 
response handlers (i.e. 401 == display login box).

When our Javascript gets the response it simply redirects the user to a page 
telling them they've successfully logged out, or whatever you want them to see. 
The only reason this works is that the browser has now cached the bogus 
username and password you sent in the AJAX request, so if/when the user then 
hits another page that requires authentication they will get the login box 
because those cached details are not valid.

To send the Authorization header with XMLHttpRequest there are username and 
password parameters to the open method: 

Hopefully this makes more sense now.


Stuart Dallas
3ft9 Ltd


Thanks to your wonderful explanation - much of which I kinda knew, just not in such detail - I have a working solution which I will show. From your latest missive I gleaned that I needed to have a script on my server that had the authenticate header included as well as my xml js function opening the connection with a user and pswd value (bogus as they were).

For those reading along:

My php script that is called from JS via xml/ajax:
//   BasicAuth_Signoff.php
//    A script used by an xml request to enforce a basic auth signoff
    header("WWW-Authenticate: Basic realm=My Bowling League Data");
    header('HTTP/1.0 401 Unauthorized');
    echo "true";
Note: the realm has to match the one used when the user signed in!

My JS xml call:
        var myreq = new XMLHttpRequest();
        urlmeth = "GET";
        myreq.open(urlmeth, url, true,"x","x");
    (just the essentials of making the call here)

In my mind I see it like this:
The php script expects authentication to occur because of the first header, and responds with the 401 because of the 2nd. The JS code calls the php script and provides the responses to the authentication request in the open statement.

Any ideas on improving this would be appreciated, but as it stands above, it's working almost exactly as I wish. The only drawback right now is that the user only has to hit enter to the first request for a following signin and he is prompted with a second signin dialog showing the last valid credentials, making the signoff not that effective. (Note: both the userid and pswd parms MUST be provided in the XML open call or IE defaults the next attempt to signon to the last working set of credentials, making the signoff even more fruitless.) Any tips on this will also be appreciated.

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