The template system has always been one of Joomla's most powerful features, but prior to Joomla 1.5 it was difficult for web design companies to ship templates with much in the way of built-in flexibility. For example, a template available in a variety of different colour schemes would often be supplied as a suite of separate template files. Some web design companies created their own methods for allowing the site administrator to change colour schemes and other template features in the Administrator, but these methods were not standardised and often involved the site administrator in editing configuration files by hand, or installing a custom component to manage the template.
This all changed with the advent of Joomla 1.5 which supported the idea of template parameters. Actually it would be more accurate to call them extension parameters as the implementation is generic for all extension types: components, modules, plugins and templates. In this chapter you will learn about how to create and use parameters in your template designs. Each of the wide range of parameter types directly supported by the Joomla Framework is described in detail, but you will also learn how to create your own custom parameter types to suit your particular needs. There is also a short reference on regular expressions as they are used in some of the template parameter types.
Introduction to template parameters
Defining a parameter in templateDetails.xmlThe templateDetails.xml file is always located in the root directory for the template. For example, for the Beez template the full path will look like:
Note that letter case is important on case-sensitive operating systems such as Linux. You can use a standard text editor (not a word processor) or an XML editor to make changes to this file.
Locate the <params> element, generally towards the end of the file. If there is no <params> element you will need to add one. This must be immediately beneath the <install> element in the XML element hierarchy. Don't forget to close the element with a </params> tag. Note that for Joomla 1.6 onwards the <install> tag is deprecated in favour of <extension>.
- See Creating a basic templateDetails.xml file for an introduction to creating a templateDetails.xml file from scratch.
- See Specification of templateDetails.xml for a detailed specification of this file.
For each parameter that you want to define, add a <param> element. This element takes a number of mandatory and optional arguments that depend on the type argument. The only truly mandatory argument is type, but name, default, description and label are common to most parameter types and name is mandatory whenever it occurs. These mandatory/common arguments are:
- type specifies the type of HTML form control used in the Template Parameters screen in the Administrator to allow the user to change the value of the parameter.
- name is the unique name of the parameter. You will refer to this name when retrieving the parameter value in the template code.
The following arguments are optional but are common to almost all parameter types:
- default is the default value of the parameter.
- description is text that will be displayed as a tooltip for the field in the Template Parameters screen in the Administrator. This is a translatable string; see Template Translations for information on how to add language translations of this string.
- label is the descriptive title of the field which will be shown to the user in the Template Parameters screen in the Administrator. This is a translatable string; see Template Translations for information on how to add language translations of this string. If the label argument is omitted it will default to the value given by the name argument.
The optional arguments depend on the parameter type. Each of the parameter types is described in detail in J1.5:Standard parameter types. If you are a developer it is also possible to create your own custom parameter types; see J1.5:Creating_custom_template_parameter_types for more information.
For example, the following extract shows a <params> section defining two parameters; one for a drop-down list of template colour variations, the other for a radio button which will allow the user to show or hide an author copyright message.
<params> <param name="templateColour" type="list" default="blue" label="Template Colour" description="Choose the template colour."> <option value="blue">Blue</option> <option value="red">Red</option> <option value="green">Green</option> <option value="black">Black</option> </param> <param name="authorCopyright" type="radio" default="1" label="Author Copyright" description="Show/Hide author copyright."> <option value="0">hide</option> <option value="1">show</option> </param> </params>
The Template Parameters screen for this example will look like this:
Note: Parameter groups are not currently supported in template parameters.
Tip: To include HTML tags in XML arguments you must encode certain special characters as follows: