I've previously written about dynamic forms in Drupal, using #states to show or hide input boxes depending on other inputs. Since then, Drupal 7 and 8 have both got the ability to combine conditions with OR and XOR operators. This makes it possible to apply changes when a form element's value does not equal something, which is not obvious at all.
Here's a quick follow-up to my original post on Dynamic forms in Drupal 7, as a reply to Wappie08, who asked me about combining conditions in the #states array to add increased control over the display of your form elements. The question: Hi James Williams, I read your blog post about d7 & #states in the FAPI which is really cool! One problem is that the information is also listed in the drupal.org example module...
When building forms, you will often want to only provide certain options if other options are chosen by a user. For example, there's no need to show the 'open link in new window' checkbox, if the 'make this into a link' checkbox hasn't been ticked. These kinds of dynamic forms haven't been easily available for Drupal... until now, with the #states for form elements in Drupal 7. Take a peek at this example of dynamic...