Login page on one domain to log in to pages on another domain

Don't ask, not my idea.

I'm assuming this is a no no.

Basically I have been working on a big project that uses a common database to serve up data to a few different websites.

For one reason or another various log in and database admin parts have been built on three different sites.

I had thought we had now settled on moving everything over to the site which is kind of the umbrella site for the others. Which I thought made absolutely good sense.

So having done a whole heap of that, the site owner then suggests having a log in page on another site (so as not to confuse the people registered), but then take them to admin pages on a different site.

I'm assuming this is a big deal breaker. Which suits me, as I think it would be less confusing with all this stuff on the same site, with logos and text to explain why it was there.

when a person logs in, the login stores data for the user in session variables.

session variables are domain based, the session created on one domain cannot be used on another domain.

you could store the sessions in hidden form elements, post the form to the other domain, and use the set session value behavior to set the sessions again on the other domain, but this will become very cumbersome to manage.

what happens if the login on domain 1, post the session details to domain to, on domain 2 they update something in the account that is stored in the session? it's easy enough to rest the session on domain 2, but now you also need to account for updating it on domain 1

Thanks Jason - I assumed it was either not possible, or if it was, it would be more trouble than it could ever be worth.