A Joomla! 1.5 Module is in its most basic form two files: an XML configuration file and a PHP controller file. The XML configuration file contains general information about the module (as will be displayed in the Module Manager in the Joomla! administration interface), as well as module parameters which may be supplied to fine tune the appearance / functionality of the module. The PHP file provides the controlling logic for the module. A very simple "Hello World" module might looking something like this.
