So, I've got the oddest problem. I have a website which a hundred or so people use, but one or two people have problems accessing it. More specifically, The access page for the site (index.php) checks for a session, and if there isn't one, begins a new one, does some init stuff, and pushes the user back to the login page.
These few users continually get pushed back to the login page, presumably because every page load their session seems to disappear.
A few hints:
I have the site runnning on two different environments with identical code bases. On one (Apache on WinXP), there is no rejection of the users, whereas on the other, a commercial web-hosting setup, there is.
(This leads me to think it may be something with certain php init values)
For users who do not have any problems, calling session_id() returns, as expected, the session_id. For the problem users, though, it returns xxx.domain.com, where xxx.domain.com is the subdomain the site is running on. No session_id at all.
There is never any resetting of session_id by any code.
I'd be happy to provide any more information that may help, but I do appreciate any insight into this matter.