What is bootstrap.php.cache?
bootstrap.php.cache is a Symfony cache file in the app directory.
It contains a number of class definitions, so Symfony no longer needs to include all those classes from their source files. This increases performance.
The composer.json normally contains a post install/update command to build the bootstrap.php.cache file:
If you didn't complete a composer update your installation may not run because of bootstrap.php.cache errors:
Warning: require_once(/vagrant/web/../app/bootstrap.php.cache): failed to open stream: No such file or directory in /vagrant/web/app_dev.php on line 20
So solve this, the composer problems should be fixed first.
The file can also be generated with: