In your analysis report, you may get the violation
A Symfony application should be bootable.
This violations means SymfonyInsight was not able to boot the Symfony application due to an
error occuring during the boot.
A lot of things could be the reason of the failure but here are the most common ones.
Your application fails to boot because of the connection to a database not accessible.
Starting databases is usually not required, nor desirable. Even if SymfonyInsight boots your application kernel to analyze it, theoritically, a local database should not be required.
Yet, in some cases you can see "Dependencies cannot be installed" or
"SymfonyInsight was not able to boot your Symfony application" error.
The reason is that SymfonyInsight always try to install and boot your
application before analyzing it. When installing your project's dependencies,
composer install command is executed. In turn, this command executes the
cache:clear command, which tries to boot the kernel of your application.
This usually indicates that Doctrine ORM is trying to guess the database server version by
querying it. This can be easily resolved by using the
server_version option to set this
value manually: https://blog.insight.symfony.com/2014/12/22/making-symfony-bootable-with-dbal-2-5.html.
If the issue is different, see "How to connect to a database".