Change php code Joomla plugin
How to change the code so that text "I am a happy plugin"  appears only in the archived items?. Thanks

This is the php code:

    <?php 
// No direct access allowed to this file
defined( '_JEXEC' ) or die( 'Restricted access' );

// Import Joomla! Plugin library file
jimport('joomla.plugin.plugin');

//The Content plugin MakePlugIn
class plgContentMakePlugIn extends JPlugin
{
    function plgContentMakePlugIn (&$subject)
    {
        parent::__construct ($subject);
    }
    function onPrepareContent (&$article, &$params, $page=0)
    {
        print "I am a happy plugin";
    }
}
?>
Change php code Joomla plugin
===

How to change the code so that text "I am a happy plugin"  appears only in the archived items?. Thanks

This is the php code:

    <?php 
// No direct access allowed to this file
defined( '_JEXEC' ) or die( 'Restricted access' );

// Import Joomla! Plugin library file
jimport('joomla.plugin.plugin');

//The Content plugin MakePlugIn
class plgContentMakePlugIn extends JPlugin
{
    function plgContentMakePlugIn (&$subject)
    {
        parent::__construct ($subject);
    }
    function onPrepareContent (&$article, &$params, $page=0)
    {
        print "I am a happy plugin";
    }
}
?>