If you don’t know what form collections are you won’t be interested in this article now. However you can read the cookbook out of curiosity and come back read this article later.
Despite the customization options, if you have to implement complex behaviors, this file may not be a solution for you. Nevertheless you can modify it to suit your needs.
Try it on your computer.
If you’ve never done form collections with Symfony before, you really should follow the cookbook in order to understand how Symfony works with form collections.
If you want to know more about what is possible, you may want to read the documentation.