WebFarms and Sessions

[eluser]kurucu[/eluser]
Tt really depends on your implementation. With load sharing across a single domain a normal session will work (database or otherwise, assuming they access the same/copies of the same database).

If he's talking about different domains accessing a common core then the browser won't share cookies with the other domains.

Then an alternative to the ajax method is to run a bunch of meta/js redirects with a token inside them that was gained from the first session start. Once you know that four different sessions are actually the representing the same user across different sites, then you just replicate anything you do on the server side across all the sessions (easiest if they are just quick sql updates in a table). Another option might be to load images in the page from each domain (if there are only a few) which access PHP scripts and send the first token in the url of the image.

Once you go down this route, however, you really should guard all protected actions with an extra password confirmation.

You might remember IE clicking across different Microsoft domains when you signed into Hotmail in the old days, it was doing a very similar thing.