Drupal 7 - Hide certain form fields of a content edit form depending on the content data

Question

In Drupal 7, is there a way to change the standard edit form for a content type based on a certain content?

For example:

I have a content type with a checkb

Answer 1

hook_form_alter is the way to do this, as explained by Mihaela, but what options do you have inside that function?

• If you want just to disable field (it will be visible, but user can't change it) you can do it like this:

  $form['field_myfield']['#disabled'] = TRUE;

• And if you want it to be hidden, but to keep value it has before editing the way to do that is:

  $form['field_myfield']['#access'] = FALSE;

I.e. hiding it (somewhere I saw someone suggesting that):

hide($form['field_myfield']);

really hides the field, but after that, when form is saved this field has empty value, validation fails, etc, so that's not a good way to do this. Hiding makes sense only if you want to print separately that field later, at some other place.