How to make the submit button not appear on form unless an option is selected from radios?

Question

I have a form with three form elements:

1. '#type' => 'radios' element having two options (Yes or No),
2. '#type' => 'submit' &
3. '#type' => 'checkbox'

When the user lands on the form page, he should only see the radios element first and can see the checkbox & submit elements only if he selects an option from radios element.

Is there a Drupal way to do this using the Form API?

Answer 1

You can use #states attribute in form api to hide submit button and check box

For Example

$form['email_canceled']['settings'] = array(
    '#type' => 'container',
    '#states' => array(

      // Hide the settings when the cancel notify checkbox is disabled.

      'invisible' => array(

       ':input[name="email_canceled_toggle"]' => array('checked' => FALSE),
      ),
    ),
  );