Creating a simple module/Developing a Basic Module

From Joomla! Documentation

< J3.x:Creating a simple module
Other languages:
Bahasa Indonesia • ‎Deutsch • ‎English • ‎Nederlands • ‎español • ‎français • ‎português do Brasil • ‎русский • ‎中文(台灣)‎
Creating a simple module

This is a multiple article series on how to create a module for Joomla! Version Joomla 3.x. You can navigate the articles in this series by using the navigation drop down menu.

Begin with the Introduction, and navigate the articles in this series by using the navigation button at the bottom or the box to the right (Articles in this series). There are 2 videos accompanying this tutorial which you can view at Basic Joomla Module Development video 1 and Basic Joomla Module Development video 2.

Modules are lightweight and flexible extensions. They are used for small bits of the page that are generally less complex and are able to be seen across different components.

You can see many examples of modules in the standard Joomla! install: - menus - Latest News - Login form - and many more.

This tutorial will explain how to go about creating a simple Hello World module. Through this tutorial you will learn the basic file structure of a module. This basic structure can then be expanded to produce more elaborate modules.

File Structure[edit]

There are four basic files that are used in the standard pattern of module development:

  • mod_helloworld.php - This file is the main entry point for the module. It will perform any necessary initialization routines, call helper routines to collect any necessary data, and include the template which will display the module output.
  • mod_helloworld.xml - This file contains information about the module. It defines the files that need to be installed by the Joomla! installer and specifies configuration parameters for the module.
  • helper.php - This file contains the helper class which is used to do the actual work in retrieving the information to be displayed in the module (usually from the database or some other source).
  • tmpl/default.php - This is the module template. This file will take the data collected by mod_helloworld.php and generate the HTML to be displayed on the page.

Creating mod_helloworld.php[edit]

The mod_helloworld.php file will perform three tasks:

  • include the helper.php file which contains the class to be used to collect the necessary data
  • invoke the appropriate helper class method to retrieve the data
  • include the template to display the output

The helper class is defined in our helper.php file. This file is included with a require_once statement:

require_once dirname(__FILE__) . '/helper.php';

require_once is used because our helper functions are defined within a class, and we only want the class defined once.

Our helper class has not been defined yet, but when it is, it will contain one method: getHello(). For our basic example, it is not really necessary to do this—the “Hello, World” message that this method returns could simply be included in the template. We use a helper class here to demonstrate this basic technique.

Our module currently does not use any parameters, but we will pass them to the helper method anyway so that it can be used later if we decide to expand the functionality of our module.

The helper class method is invoked in the following way:

$hello = modHelloWorldHelper::getHello($params);

Completed mod_helloworld.php file[edit]

The complete mod_helloworld.php file is as follows:

 * Hello World! Module Entry Point
 * @package    Joomla.Tutorials
 * @subpackage Modules
 * @license    GNU/GPL, see LICENSE.php
 * @link       http://docs.joomla.org/J3.x:Creating_a_simple_module/Developing_a_Basic_Module
 * mod_helloworld is free software. This version may have been modified pursuant
 * to the GNU General Public License, and as distributed it includes or
 * is derivative of works licensed under the GNU General Public License or
 * other free or open source software licenses.

// No direct access
defined('_JEXEC') or die;
// Include the syndicate functions only once
require_once dirname(__FILE__) . '/helper.php';

$hello = modHelloWorldHelper::getHello($params);
require JModuleHelper::getLayoutPath('mod_helloworld');

The one line that we haven’t explained so far is the defined('_JEXEC') or die; line. This line ensures that this file is being invoked from the Joomla! application. This is necessary to prevent variable injection and other security vulnerabilities.

Creating helper.php[edit]

The helper.php file contains the helper class that is used to retrieve the data to be displayed in the module output. As stated earlier, our helper class will have one method: getHello(). This method will return the ‘Hello, World’ message.

Here is the code for the helper.php file:

 * Helper class for Hello World! module
 * @package    Joomla.Tutorials
 * @subpackage Modules
 * @link http://docs.joomla.org/J3.x:Creating_a_simple_module/Developing_a_Basic_Module
 * @license        GNU/GPL, see LICENSE.php
 * mod_helloworld is free software. This version may have been modified pursuant
 * to the GNU General Public License, and as distributed it includes or
 * is derivative of works licensed under the GNU General Public License or
 * other free or open source software licenses.
class ModHelloWorldHelper
     * Retrieves the hello message
     * @param   array  $params An object containing the module parameters
     * @access public
    public static function getHello($params)
        return 'Hello, World!';

There is no rule stating that we must name our helper class as we have, but it is helpful to do this so that can be easily identified and located. Note that it is required to be in this format if you plan to use the com_ajax component.

More advanced modules might include database requests or other functionality in the helper class method.

Creating tmpl/default.php[edit]

The default.php file is the template which displays the module output.

The code for the default.php file is as follows:

// No direct access
defined('_JEXEC') or die; ?>
<?php echo $hello; ?>

An important point to note is that the template file has the same scope as the mod_helloworld.php file. What this means is that the variable $hello can be defined in the mod_helloworld.php file and then used in the template file without any extra declarations or function calls.

Creating mod_helloworld.xml[edit]

The mod_helloworld.xml is used to specify which files the installer needs to copy and is used by the Module Manager to determine which parameters are used to configure the module. Other information about the module is also specified in this file.

The code for mod_helloworld.xml is as follows:

<?xml version="1.0" encoding="utf-8"?>
<extension type="module" version="3.1.0" client="site" method="upgrade">
    <name>Hello, World!</name>
    <author>John Doe</author>
    <description>A simple Hello, World! module.</description>
        <filename module="mod_helloworld">mod_helloworld.php</filename>

Manifest files explains the technical details of the elements used in the XML file.

You will notice that there are two additional files that we have not yet mentioned: index.html and tmpl/index.html. These files are included so that these directories cannot be browsed. If a user attempts to point their browser to these folders, the index.html file will be displayed. These files can be left empty or can contain the simple line:

<html><body bgcolor="#FFFFFF"></body></html>

which will display an empty page.

Since our module does not use any form fields, the config section is empty.

Installing and Viewing the Module[edit]

To install the module, zip up the parent directory of your source files, to create a file called mod_helloworld.zip. Note that it needs to be a .zip file because the server needs to be able to extract it using Apache's mod_zlib library. Go into Joomla admin, to the Extensions / Manage / Install form, click on the Update Package File tab, and upload your zip file. You should find that the module installs ok. If it doesn't, then compare carefully your code with the code above, and ensure your source code files are named correctly. To make the module visible on your site web pages go into the Extensions / Modules listing and click on the Hello World module to edit it.

  1. set the Status to Published
  2. select the Position where the module should appear (if you're unsure about which Position to set, then navigate to Extensions / Templates / Styles, check which template is assigned on your web pages, then follow this guide to finding the module positions).
  3. on the Menu Assignment tab set the Module Assignment to "On all pages"

Save and Close your edit form. Now if you navigate to your site you should see "Hello, World!" displayed in your chosen module position.


Module development for Joomla! is a fairly simple, straightforward process. Using the techniques described in this tutorial, an endless variety of modules can be developed with little hassle.