Work with Doctrine Migration in Symfony

To update your schema, classes, database without losing data, try to do this...

1. Change your schema.yml file.
2. Use the symfony doctrine:generate-migrations-diff command to generate the differences between the current classes and the changed schema. These changes are converted by Doctrine into a migrations files, you can find them in the lib/migration directory. In the filename you will see a version number.
3. Type the symfony doctrine:migrate x command to update your database. x is the version number you found in the filename of the last migration file.
4. Type the symfony doctrine:build --all-classes command to generate new classes for symfony.

Symfony will create a migration_version table in the database to store the current migration version number.