Last updated May 16, 2019

Sometimes you need to add additional processing of input to forms where your module doesn't implement the form controller. In order to do this you can use the #submit property of the root level $form element, or of a specific button on a form, to add one or more callbacks. These functions, or methods, will be automatically called when the Form API is processing a submitted form and give your custom code an opportunity to do whatever it needs to do.

In this tutorial we'll:

  • Look at alternative ways to affect the submission handling of a form like #submit callbacks

By the end of this tutorial you should know how to add a #submit callback to an entire form, or a specific button in a form.