A bunch of WordPress sites broke without any errors and without that usual “Your site is experiencing technical difficulties” notification. The sites were only displaying a blank White Screen Of Death.
Enabling wp_debug didn’t show anything at all, which is pretty unusual. But in the error log I found Failed opening required '/home/user/public_html/wp-content/advanced-headers.php
which is just as it sounds, there is a file that must be included but it couldn’t be opened.
In fact the file is completely missing in each case. I think the error is being caused by some sort of issue with the Really Simple SSL plugin, I remember spotting something about it, but can’t find it again.
No worries, the fix is trivial. Simply create an empty file named advanced-headers.php
in the /wp-content directory. I am not sure what the original contents were or what it is supposed to do, but at least this gets the site up again.
Here’s a cautionary tale. All the customers who subscribe to the WordPress Management Thingy had this spotted and then fixed (for free, of course) because it showed up in my management dashboard. Cheap insurance I reckon. Just saying ;o)