Hmmm.
This appears to be a bug with certain versions of PHP, the programming language used by WordPress and its plugins, when certain features are enabled, under certain website page load conditions.
PHP Bug Report: https://bugs.php.net/bug.php?id=59298
Unfortunately, I can’t do anything about PHP bugs. Tweet This is beholden to any and all PHP idiosyncrasies and flaws.
However, others stymied by this PHP bug have made one or more changes on their end that worked for them. Some of the more common and promising fixes seemed to be:
- Disable the APC caching feature of PHP.
- Upgrade PHP to a more recent release.
- Preventing PHP’s APC caching from caching the problematic files using APC filters.
However, I can not recreate this problem so I can’t give specific feedback on which of those methods, if any, work. I can only repeat anecdotal comments from my research into the bug.
Implementing any of these potential fixes will be dependent on your web hosting provider. You will need to look into their documentation or contact them to see if they are feasible, and if so, how to accomplish them.
My personal first attempt, and likely the easiest, would be to upgrade PHP if not using the latest available. Many, many web hosts choose to use older versions of PHP by default (5.2.x and 5.3.x are most popular despite their age), but have mechanisms for using more recent versions (5.6.x is the current latest release). At a minimum, I would find what version of PHP my web host had me currently using, then upgrading by at least one minor version number (the middle number). For example, if my version were 5.3.4, I would look to upgrading to no less than 5.4.0. Ideally, however, I’d upgrade to the absolute latest available through my web host.
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This bug has prompted me to accelerate some research into techniques I have wanted to do for a while, the net result of which may allow me to altogether circumvent the important code that PHP is mishandling.
However, there are a lot of potential consequences to the changes I am envisioning, and the changes are moderately complex. As such, I have no timeframe for when and if I will complete this, and at this time, I’m only making an educated guess as to its ability to circumvent the problem. If possible, I don’t suggest relying on this being a fix, in lieu of the suggestions above.