If your server crashed or old files were restored by accident, or some files got corrupt (you know how that can sometimes happen), your website might experience some glitches, or worse, the dreaded “Server 500 Error”. If you are running Symfony and experiencing errors that are not typical, you might need to rebuild the bootstrap.cache.php file. From the command line, go to your Symfony root folder and paste this command into the CLI:

php ./vendor/sensio/distribution-bundle/Sensio/Bundle/DistributionBundle/Resources/bin/build_bootstrap.php

Another issue is to comment out any of your ‘%kernal_debug%’ lines, or set to default and “%kernel_debug%’ settings in your production config.yml settings if you are operating in a production environment and restricted debugging on it.