So, I've wanted to capture this information for a current project and my searches led me to this thread, among others. Unfortunately for me, I don't have PHP or ASP options available to me so that leads me to seeking out a client side solution. Normally, that doesn't exist but I *MAY* have found a surrogate solution that I wanted to share. This is still unproven but the pieces are there. Anyways, you might be able to extract user information using Sharepoint, provided your organization uses it. I found many helpful sites as I descended the rabbit hole of Sharepoint web searches but this site which discusses the Javascript Object Model for Sharepoint 2010 was helpful for what I will share. My testing has ground to a halt because my organization uses Sharepoint 2010 and the following code solution will only work with Sharepoint 2013 or above (presumably).
Anyways, to get started, you need to add five JS script references into your project (my source for this was here😞
<script src="/_layouts/1033/init.js"></script>
<script src="/_layouts/MicrosoftAjax.js"></script>
<script src="/_layouts/sp.core.js"></script>
<script src="/_layouts/sp.runtime.js"></script>
<script src="/_layouts/sp.js"></script>
The paths must be adjusted to your Sharepoint set up. Our organization's Sharepoint base URL is "https://team/depts/....." so the previous code was modified to the following:
<script type="text/javascript" src="https://team/_layouts/1033/init.js" ></script>
<script type="text/javascript" src="https://team/_layouts/MicrosoftAjax.js"></script>
<script type="text/javascript" src="https://team/_layouts/sp.core.js" ></script>
<script type="text/javascript" src="https://team/_layouts/sp.runtime.js" ></script>
<script type="text/javascript" src="https://team/_layouts/sp.js" ></script>
BTW, I think the order of the Sharepoint JS script references DOES matter. I kept getting console errors until I specified them in the order shown above. With that out of the way, it's time for the JS code. There's not much code to it, really-
var targetWeb;
function spUserName() {
var theSpCc = new SP.ClientContext('<path to sharepoint page>');
targetWeb = theSpCc.get_web();
theSpCc.load(targetWeb);
theSpCc.executeQueryAsync(Function.createDelegate(this,this.onQuerySucceeded),Function.createDelegate(this,this.onQueryFailed));
}
function onQueryFailed(sender, args) {
alert('Request failed. \nError: ' + args.get_message() + '\nStackTrace: ' + args.get_stackTrace());
}
function onQuerySucceeded() {
var theUser = targetWeb.get_currentUser();
var theUsername = theUser.get_loginName();
var message = "Web retrieved:";
message += "\n Title: " + targetWeb.get_title();
message += "\n ID: " + targetWeb.get_id();
message += "\n Language: " + targetWeb.get_language();
message += "\n UI Version: " + targetWeb.get_uiVersion();
message += "\n Description: " + targetWeb.get_description();
message += "\n Created: " + targetWeb.get_created();
message += "\n\n And you are: " + theUsername ;
alert(message);
}
I haven't been able to fully test this because Sharepoint 2010 (our current version) only supports relative path names when creating a ClientContext instance. My web app won't be hosted on the Sharepoint server so this code won't work. In Sharepoint 2013, however, full paths are accepted so I feel that this *should* work.
Lastly, there is another Sharepoint related option but I still have a sticking point to implementing it. You can use AJAX on a particular Sharepoint List URL to retrieve a user's information (provided you know their user ID):
Sharepoint 2010:
https://<path to sharepoint page>/_vti_bin/ListData.svc/UserInformationList(theUserID)
Sharepoint 2013:
http://<path to sharepoint page>/_api/Web/GetUserById(theUserID)
Of course, the problem here is that you need to know, or figure out a way to reverse engineer, a user's user ID within Sharepoint. This was my original tact but I couldn't quite figure out how to extract his programatically. If you're on a Sharepoint page, simply type "_spUserId" in the console and you'll get your ID.
Anyways, I wanted to throw this out there for the record. I know it won't help everyone but maybe it helps a few! If anyone does get it to work, I'd love to hear about it!
Steve
Unfortunately at this time PHP/JQuery are not installed on this Windows server. I wonder if this can be rewritten using a Python or ASP script called from Javascript. 
