[Plugin: WP Super Cache] PHP warnings & white screen of death

Using the debug level in the admin page I set up email notifications. Most look fine. The following is the only one that appears to show an error:

Buffer is blank. Output buffer may have been corrupted by another plugin or this is a redirected URL. Look for text ‘ob_start’ in the files of your plugins directory.

The problems intensified so I have disabled WPSC for now. No white screens in the two hours since I did so, so I’m pretty sure WPSC was at least part of the problem.

I am still interested if you have a suggestion or something to share.

Did you install any new plugins recently? As the debug message said, “look for ‘ob_start’ in your plugins directory” …

In my ongoing conversation with myself…

Going over donncha’s troubleshooting points again I came across this one (the very last):

The “white screen of death” or a blank page when you visit your site is almost always caused by a PHP error but it may also be caused by APC. Disable that PHP extension if you have trouble and replace with eAccelerator or Xcache.

This would explain why I’ve been seeing these white screens of death without a PHP error at exactly the same time. But it was still happening with WPSC disabled. Then I found Mark Jaquith’s article from 2006 about a conflict between wp-cache and APC – and I still had wp-cache enabled in wp-config.

I have now disabled APC to see whether that stops the WSODs. If it does, then I’ll give Mark’s solution a bash and re-enable WPSC too.

Apologies donncha, missed your reply. Yes, I did check for that file but it doesn’t exist.

My current theory is that APC is the culprit.

It’s quite possibly APC. That will generate segmentation fault errors in your Apache error logs if it is the case.

You should still search for the text “ob_start” in the files in your plugins folders. ob_start isn’t a file there, it’s a command that is sometimes not used correctly.

Thanks donncha. I get it now with ‘ob_start’. I will check that out and see whether it eliminates the errors when I re-enable WPSC.

The interesting thing is that there are no signs of the APC segfaults in the error logs. Apparently that is because WP-Cache suppresses them with the error silencing “@”.

BTW, as far as I can tell without APC and WPSC there have been no more WSODs.

So I’ll do some testing with WPSC and Mark’s APC fix and report back here later.

Any news one this?