Joshua Thijssen has a new post to his site looking at a way to dynamically modify forms in a Symfony2-based application. Form handling can be a bit tricky (especially with more complex elements), and modifying them on the fly can be even more difficult.

Sometimes (or actually, a lot of the time), handling forms will go beyond the basics. And even though symfony2 gives you out-of-the-box a really clean way of creating forms, it sometimes just isn’t enough. Fortunately, you are not alone in writing forms, and many posts exists with information on how to handle complex forms. In this post, I will try and demonstrate how to create a dynamic form where you can select a city based on the chosen province.

His example lets the user pick their province and then populates the other select with cities in that area. He includes the code for the form to create these two selects and how to pull out the list of provinces to populate the first. He goes through each part of the example code explaining the methods, what they're doing and how a pre-submit event can be used to populate the second list.