Heres a bit of information on module development.

Screen.modules.edit.15 - Joomla! Documentation - http://docs.joomla.org/Screen.modules.edit.15
Screen.modules.15 - Joomla! Documentation - http://docs.joomla.org/Screen.modules.15

See also

Core hacks are bad, a way around core hacks is to code a plugin or do an override. Plugins replace content or add content or modify content. For instante we have a recaptcha plugin, enabling it and configuring it can put a recaptcha on your contact page. As a core hack, you would have to modify components/com_contact/somefiles here... So if a new version of joomla happens to upgrade that area your core hack just broke. As a plugin it will never break.

Tutorial:Plugins - Joomla! Documentation - http://docs.joomla.org/Tutorial:Plugins
Screen.plugins.15 - Joomla! Documentation - http://docs.joomla.org/Screen.plugins.15

Available extension parameter types and how to use them When you create an extension (component, module, plugin or template) you can implement parameters in the .XML file. With this parameters you can set options, and use them in the main file, the .PHP file. There are 20 extension parameter types available in Joomla! 1.5. You can use them easily and in this document you will find a description for all of them. You can also add your own parameters, but this will not be described in this article.

Table of contents

1. XML file
2. Parameters
3. Core parameters
4. Calendar
5. Category
6. Editors
7. File list
8. Folder list
9. Help sites
10. Hidden
11. Image list
12. Language
13. List
14. Menu
15. Menu item
16. Password
17. Radio
18. Section
19. Spacer
20. SQL
21. Text
22. Text area
23. Time zones

XML file
You need an XML file for every extension. It is used mainly to install the extension. A particular XML file looks like this:

<?xml version="1.0" encoding="utf-8"?>
<install version="1.5" type="extension type">
<name>Name of your extension</name>
<creationDate>Created Date</creationDate>
<author>Your name</author>
<authorEmail>Your e-mail address</authorEmail>
<authorUrl>Your website</authorUrl>
<copyright>Copyright</copyright>
<license>License, for example GNU/GPL</license>
<version>Version of the extension</version>
<description>Description of the extension</description>
<files>
<filename>add the files between those tags</filename>
</files>
<languages>
<language tag="en-GB">Language file</language>
</languages>
<params>
Place the parameters between these tags.
</params>
</install>

Parameters
The parameters should be placed between the <params> and </params> tags. You can also add groups. For example, the 'Advanced' group. This will look like this:
<params>
'Normal' parameters
</params>
<params group="advanced">
Advanced parameters
</params>

Note: You can not add groups to templates.

Core Parameters
There are 20 parameter types available within your Joomla! 1.5 installation.

These are:
Calendar, Category, Editors, File list, Folder list, Help sites, Hidden, Image list, Language, List, Menu, Menu item, Password, Radio, Section, Spacer, SQL, Text, Text area and  Time zones, and will be described here in detail.
Each one is described in the following order:

• Description
• Screen shot of output
• XML file
• Implementation in PHP file
  • Reference

Calendar
Description: This parameter shows a text box where you can fill in the date. You can also choose the date from a calendar, which pops up after you clicked on the icon next to the text box.
Screen shot:

XML file: Use the following code in the XML file to create a parameter like this.
Name: The name used to implement  in the PHP file.
Type: For a calendar parameter, use 'Calendar'.
Default: The default date.
Label: The name displayed at the output of the parameter.
Description: The description displayed as a tool tip.
Format: The format of the date.

<param name="calendar" type="Calendar" default="5-10-2008" label="Calendar" description="" format="%d-%m-%Y"  />

PHP file:

For example, get the parameter, named publish_up, like this:

$publish_up = new JDate($row->publish_up);

Reference: administrator\components\com_content\admin.content.html.php, 122-168

Category
Description: This parameter shows a drop down list of categories from a section.
Screen shot:

XML file: Use the following code in the XML file to create a parameter like this.

Name: The name used to implement  in the PHP file.
Type: For a category parameter, use 'Category'.
Label: The name displayed at the output of the parameter.
Description: The description displayed as a tool tip.
Section: The section ID number, can be found in the Section Mana

<param name="category" type="Category" label="Category" description="" section="3"  />

PHP file:

For example, get use the parameter, named category, like this:

$category[$section->id][]

Reference: administrator\components\com_content\controller.php, 452-530

Editors
Description: This parameter shows a drop down list of the available WYSIWYG editors.
Screen shot:

XML file: Use the following code in the XML file to create a parameter like this.

<param name="editors" type="Editors" default="" label="Editors" description=""  />

Name: The name used to implement  in the PHP file.
Type: For an editor parameter, use 'Editor'.
Default: The default editor.
Label: The name displayed at the output of the parameter.
Description: The description displayed as a tool tip.

PHP file:

For example, get the parameter, named editors, like this:

$this->lists['Editors']

Reference: administrator\components\com_config\controllers\application.php, 86

File list
Description: This parameter shows a drop down list of files from a certain directory.