Recently, I updated from 8.1.8 to 8.1.10 (via
composer update). In my local environment (running scotchbox, PHP 5.6.14), it runs fine. When deployed to the staging server (running CentOS 6.7, PHP 5.5.17), the site returns a 500 and writes the following to error_log:
PHP Fatal error: Class 'Drupal\Core\Site\Settings' not found in /home/[site]/public_html/drupal/core/lib/Drupal/Core/DrupalKernel.php on line 964
I copied basically everything except the /sites/ directory, so I don't think I'm missing anything.
I tried restarting httpd to no avail.
It seems like a problem with the autoloader and possibly due to the PHP version mismatch. There are many layers between autoload.php and the DrupalKernel.php bootstrap process. I'm at a loss as to what's going on here. Any help would be appreciated.