In the latest release of Symfony 3 namely the 3.4 version, the default structure and dependencies of an empty project changed. One of the changes that affects developers that want to install FOSUserBundle, is the inexistence of the Twig templating service that FOSUserBundle requires.
If you really want to implement the FOSUserBundle in your project, you will need to satisfy the necessary dependencies. In this case, you will need to install the templating component of Symfony with composer using the following command:
Is very important that if you are using Symfony 3.4, to install as well the latest 3.4.x version of the templating component as upcoming version are compatible only with Symfony 4.x. If you install the component using only
composer require symfony/templating.
composer require symfony/templating v3.4.2
After installing this component, enable the twig template engine in your config.yml file under the framework key:
# app/config/config.yml framework: templating: engines: ['twig']
Finally clear cache if necessary and the problem shouldn't appear anymore.
Happy coding !