Use ctools modal to display content in special modal

ctools_modal_example.php

<?php
/**
 * @file Custom modal using ctools modal window
 * more infor in sites/modules/ctools/help/modal.html your local drupal's installation
 */

/**
 *  Implements of hook_menu()
 */
function custom_popup_menu() {
  $items['modal/%ctools_js/%'] = array(
    //'title' => 'Popup',
    'page arguments' => array(1, 2),
    'page callback' => 'module_modal_page',
    'access callback' => TRUE,
    'type' => MENU_NORMAL_ITEM,
  );
  return $items;
}

/**
 * A modal page callback.
 */
function module_modal_page($js = NULL, $other_params_if_needed) {
  if ($js) {
    // Required includes for ctools to work:
    ctools_include('modal');
    ctools_include('ajax');
  }
  $modal_title = '';
  $modal_content = '';
  // use ctools_modal_render()
  return ctools_modal_render($modal_title, $modal_content);
}

/**
 * Implements hook_init().
 */
function module_page_alter(&$page) {
  // use any other hook, function to attach below elements

  // Include the CTools tools that we need.
  ctools_include('ajax');
  ctools_include('modal');
  // Add CTools' javascript to the page.
  ctools_modal_add_js();
  // set modal style properties
  $module_style = array(
    'module-modal-style' => array(
      'modalSize' => array(
        'type' => 'scale',
        'width' => 0.4,
        'height' => 0.3,
        'addWidth' => 0,
        'addHeight' => 0,
        'contentRight' => 0,
        'contentBottom' => 0,
      ),
      'modalOptions' => array(
        'opacity' => .8,
        'background-color' => '#000',
      ),
      'animation' => 'slideDown',
      'modalTheme' => 'custom_popup_modal',
      // set custom close button and throbber
      'throbber' => theme('image', array(
        'path' => ctools_image_path('ajax-loader.gif', 'module'),
        'alt' => t('Loading...'),
        'title' => t('Loading')
      )),
      'closeImage' => theme('image', array(
        'path' => ctools_image_path('modal-close.png', 'module'),
        'alt' => t('Close window'),
        'title' => t('Close window')
      )),
    ),
  );

  // Add the settings array defined above to Drupal JS settings:
  drupal_add_js($module_style, 'setting');
  // add js file in js directory
  ctools_add_js('module', 'module');
  // add css file in css directory
  ctools_add_css('module', 'module');

  $href = 'modal/ajax/' . $other_params_if_needed;
  // generate link to click to the class: ctools-modal-module-modal-style is important
  $link = ctools_modal_text_button($name, $href, t('Display @name', array('@name' => $name)), 'ctools-modal-module-modal-style');
  // attach that link somewhere in the page content
}
//------------------------------------------------------
// Place in JS file
//------------------------------------------------------
/**
 * Provide the HTML to create the modal dialog.
 */
(function ($) {
    Drupal.theme.prototype.custom_popup_modal = function () {
        var html = '';
        html += '<div id="ctools-modal" class="popups-box">';
        html += '  <div class="ctools-modal-content ctools-modal-custom_popup-modal-content">';
        html += '    <span class="popups-close"><a class="close" href="#">' + Drupal.CTools.Modal.currentSettings.closeImage + '</a></span>';
        html += '    <div class="modal-scroll"><div id="modal-content" class="modal-content popups-body"></div></div>';
        html += '  </div>';
        html += '</div>';
        return html;
    }
})(jQuery);