title: Drupal7 Forms API: Ajax button not firing callback
body: <p>I'm really stumped here. I've an ajax form with a button - actually, the one below has both a button and a select object, both calling the same callback function.</p>
  
  <p>What I want: the button to call the callback, but not submit the form.</p>
  
  <p>What I have: the select calls the callback just fine, but the submit button doesn't do <em>anything.</em> </p>
  
  <p>Thoughts?</p>
  
  <pre><code>function my_module_pane_checkout_form($form, $form_state, $checkout_pane, $order) {
    $pane_form = array(); 
  
    $pane_form['codes'] = array(
      '#prefix' =&gt; '&lt;div id="codes-fieldset-wrapper"&gt;',
      '#suffix' =&gt; '&lt;/div&gt;',
    );
  
    $pane_form['codes']['add_code_0'] = array(
      '#type' =&gt; 'radios',
      '#options' =&gt; array(1 =&gt; 'One', 2 =&gt; 'Two'),
      '#ajax' =&gt; array(
        'callback' =&gt; 'my_module_pane_callback',
        'wrapper' =&gt; 'codes-fieldset-wrapper',
      ),
      '#default_value' =&gt; 1,
    );
  
    $pane_form['codes']['add_code'] = array(
      '#type' =&gt; 'submit',
      '#value' =&gt; 'Add Code',
      '#ajax' =&gt; array(
        'callback' =&gt; 'my_module_pane_callback',
        'wrapper' =&gt; 'codes-fieldset-wrapper',
      ),
    );
  
    return $pane_form;
  }
  
  function my_module_pane_callback($form, $form_state) {
    watchdog('php', 'inside callback');
    return $form['my_module'];
  }
  </code></pre>