app-init exits

[dutchiexl]

I am getting this info, then the container freezes:
INFO exited: app-init (exit status 1; not expected)

I run the following command:
docker run --name my-project -v ~/my-project:/var/app -P --link mysql56:mysql -e APP_CREATE_PROJECT="symfony/framework-standard-edition" -it phpmentors/symfony-app:php55

[iteman]

Could you explain more detail?