And it looks like the problem is solved. Ruben was correct - the Sessions files were not being updated. The Control Panel had the correct folder location in "Paths and Database", as well as the [Sessions] section of the PHP.INI file.
However, there was also a .USER.INI file created at the same date/time that the problem started. As I mentioned, BlueHost had me use the "MultiPHP INI Editor" to update the PHP.INI file. It also appears to update .USER.INI, and even create it if it doesn't exist. It also populates it with a lot of extraneous, default values.
Worse, it seems to create mistakes in the process. It appears to be pulling in default values from somewhere, and then puts quotes around the value and the adjoining comment. This makes the comment part of the value despite the semi-colon. For example, this is one line as it originally appeared:
session.save_path = "/tmp ; argument passed to save_handler"Checking PHP Info showed the value for "session.save_path" as "/tmp ; argument passed to save_handler". Not only is it pointing to the wrong folder (/tmp), it also thinks the comment is part of the folder name. When I put in the correct folder path name and moved the close quote from the end of the comment to the end of the path name, resulting in this:
session.save_path = "/home/cessnaon/public_html/forum/sessions" ; argument passed to save_handler...the forum immediately started working again as before.
Now the post-mortem begins. I'm reminded of the following joke:
“Six Stages of Debugging”: 1) That can't happen.
2) That doesn't happen on my machine.
3) That shouldn't happen.
4) Why does that happen?
5) Oh, I see.
6) How did that ever work?
Right now I'm at Stage Six. Does .USER.INI override PHP.INI values? Where did .USER.INI (or its defaults) come from? If it was always present, how did it ever work before? What's really confusing me is the original problem I was trying to solve that precipitated this whole thread - namely, how to update max_input_vars from 1000 to 3000. I have that entry in every PHP.INI file I can find. Yet, the only one that matters is the one in .USER.INI.
In the end it's working, but I don't fully understand how which leaves me with the vaguely uncomfortable feeling I'm overlooking something.
In any event - thank you all for your help. Especially Ruben - if you're ever in Connecticut I owe you a beer (or other beverage of choice). Or a sight-seeing flight over NYC. Your choice.
