This ticket is for handling form input, validating the input values and transmitting back errors, if any, back to the form view (with rest of the input data pre-populated).

These errors could, for example, be - duplicate program name/event name, incorrect usernames, incorrect dates, any other incorrect event data etc.

I don't know to what extent Symfony automates this for you. Here's a reference for how we did this with Slim for iegreview app.