Plugins are a nice way to extend the functionality of Smarty.  You can create plugins for (functions, modifiers, prefilters, postfilters, and output filters).  This tutorial will cover the creation of a very simple plugin.  Smarty has excellent documentation and already a wealth of plugins available at http://smarty.php.net/contribs/plugins/

This plugin can be used on a live site, but it isn't very useful.  It is only to demonstrate how to create plugins.  Our plugin will take a name and return a message to the user. 

1.)  Name your file function.function_name.php and place it in your plugins directory
          - Ours will be named function.welcome_message.php

2.)  Inside the code you should have a function named the same as your php file
          - function smarty_function_welcome_message($params, &$smarty){

3.)  The body of the function will perform some activity with the parameter (name) that was passed in. 
      In this case output a mesage
          - return 'Hello ' . $params['name'] . ' we are happy that you are visiting our website';}

4.)  Now you need to invoke the plugin from your tpl file
          - {welcome_message name='Marion Consulting'}

5.)  You should receive the following output
          - Hello Marion Consulting we are happy that you are visiting our website

 

Good luck!