Hacked to show sequence of events in AJAX

Hacked_ajax_example.php

/**
 * A very basic form which with an AJAX-enabled submit.
 *
 * On submit, the markup in the #markup element is updated.
 */
function ajax_example_submit_driven_ajax($form, &$form_state) {
  if (empty($form_state['sequence'])) {
    $form_state['sequence'] = 0;
  }
  else {
    $form_state['sequence']++;
  }
  $form['box'] = array(
    '#type' => 'markup',
    '#prefix' => '<div id="box">',
    '#suffix' => '</div>',
    '#markup' => '<h1>Initial markup for box</h1>',
  );

  $form['submit'] = array(
    '#type' => 'submit',
    '#ajax' => array(
      'callback' => 'ajax_example_submit_driven_callback',
      'wrapper' => 'box',
      'name' => 'submit1',
    ),
    '#value' => t('Submit'),
  );
  $form['sequence'] = array(
    '#type' => 'markup',
    '#markup' => '<h3>Sequence on form build is ' . $form_state['sequence'] . '</h3>',
  );

  return $form;
}

function ajax_example_submit_driven_ajax_submit($form, &$form_state) {
  $form_state['sequence']++;
  drupal_set_message('Submit handler fired. Sequence = ' . $form_state['sequence']);
}

/**
 * Select the 'box' element, change the markup in it, and return it as a
 * renderable array.
 *
 * @return renderable array (the box element)
 */
function ajax_example_submit_driven_callback($form, $form_state) {
  // In most cases, it is recomended that you put this logic in form generation
  // rather than the callback. Submit driven forms are an exception, because
  // you may not want to return the form at all.
  $element = $form['box'];
  $element['#markup'] = "Clicked submit ({$form_state['values']['op']}): " . date('c');
  $form_state['sequence']++;
  $element['#markup'] .= " AJAX callback Sequence=" . $form_state['sequence'];
  return $element;
}