PHP script randomly fails

[rathrw]

Okay... I've exhausted my own resources, and am finally seeking out help, figured this was a good place to do it.

Here are the details. I have an e-commerce system that I wrote, and have been tinkering with/upgrading for the past 5 years. The section in question is a password restricted area that uses sessions to maintain the identity of the user in order to associate them with their shopping cart which is stored in a MySQL database. 99% of the time, it works flawlessly.

Every now and then, sometimes 3 times a week, sometimes it doesn't happen for a month, the commerce system will complete an order and send it out without the user's identity information which should have been held in the session. Error logs show nothing happening when this problem occurrs, and my conversations with the users haven't shown me any common thread.

I've also been unable to replicate the problem to diagnose and troubleshoot it myself. Another note... this never happened until I switched to a new hosting service, site5.com. They deny that it could be anything server-side causing the problem.

Any thoughts on where in my scripts I should look to find out where the drop is happening?

Alex

[RossC0]

Well if its something thats just stored in the session thats failing every so often but normally the code works fine.

It suggests to me that its not a code issue but a php setting / memory issue - the session might be getting too big and parts are being replaced with new data.

[rehfeld]

your not losing the session id right? because if your still getting the order which is stored in the db and its associated w/ the sid, the sid couldnt be changing.

does it look like your losing all session data, or just parts of it?

i would put some checkpoints in place.

like for example, if on step 3 of the checkout process or whatever, there SHOULD be some specific variables set in the session, and you find that they arent, make a log of it.

another option might be to put error_reporting() to E_ALL but display errors off, and log all errors. this should let you see all undefined variables and indexes, and you could define a custom error handler to add the approriate info to the error entry to help you locate it.

that wouldnt work if you use isset() and empty() religiously though. but if you dont, that would be a very easy way to look at your entire script instead of manually inserting checkpoints.

[rathrw]

The only things stored in session variables are the user's ID, and a drop ship address if they use it. Here's what's odd. I've had users check out, and I'll get the drop ship address, but not their account number (so I don't know who actually placed the order). So somehow, the system is associating something in the database with the session because the cart contents are there.

I like the idea of the error logging using error_reporting() and custom error messages. I'll have to do some research on how to implement that as it's not something I've ever messed with. I've always pretty much learned just enough to do what I need to do.

I never actually use isset() or empty()... I'm pretty bad about that.

Thanks for the tips!