Drupal 7 Ctools modal example

ctewls.module

<?php
/**
 * @file
 * Ctewls module
 */

/**
 * Implementation of hook_menu().
 */
function ctewls_menu() {
  $items = array();
  $items['ctewls'] = array(
    'title' => 'Show me some CTools magic!',
    'page callback' => 'ctewls_main',
    'access callback' => TRUE,
  );
  $items['ctewls/%ctools_js/popup'] = array(
      'title' => 'Hello World',
      'page callback' => 'ctewls_popup',
      'page arguments' => array(1),
      'access callback' => TRUE,
      'type' => MENU_CALLBACK,
  );
  return $items;
}

/**
 * Page call back for /ctewls path
 */
function ctewls_main() {
  $output = '';

  ctools_include('modal');
  ctools_modal_add_js();

  $output = '<p style="margin-top: 100px;"><a href="/ctewls/nojs/popup" class="ctools-use-modal">hello modal</a></p>';
  return $output;
}

/**
 * Page/modal callback for /ctewls/nojs/popup
 */
function ctewls_popup($js = NULL) {
  $title = t('I haz pop');
  $output = '<p>' . t('Hello from CTewls world') . '</p>';
  if ($js) {
    ctools_include('modal');
    ctools_modal_render($title, $output);
  }
  else {
    drupal_set_title($title);
    return $output;
  }
}