Обьясните что к чему - Разработка расширений для Joomla 1.5

<?php

/** ensure this file is being included by a parent file */
defined( '_JEXEC' ) or die( 'Restricted access' );

$mainframe->registerEvent( 'onPrepareContent', 'pluginAddPhp' );


function pluginAddPhp( &$row, &$params, $page=0  )
{
 	// expression to search for
 	$regex = '/{(rdaddphp)\s*(.*?)}/i';

 	$plugin =& JPluginHelper::getPlugin('content', 'rd_addphp');

 	if (!JPluginHelper::isEnabled('content', 'rd_addphp')  ) {
		$row->text = preg_replace( $regex, '', $row->text );
		return;
	}

	// find all instances of plugin and put in $matches
	$matches = array();
	preg_match_all( $regex, $row->text, $matches, PREG_SET_ORDER );

	foreach ($matches as $elm) {

		parse_str( $elm[2], $args );
		$phpfile=@$args['file'];
		$output = "";
		if ( $phpfile ) {
			$phpfile = JPATH_ROOT . DS . $phpfile;
			if (file_exists($phpfile)) {
				ob_start();
				include($phpfile);
				$output .= ob_get_contents();
				ob_end_clean();
			} else {
				$output = "File: $phpfile don't exists";
			}
		}
		$row->text = preg_replace($regex, $output, $row->text, 1);

	}
	return true;
}
/* EOF */
?>

{rdaddphp file=file.php}

preg_match_all( $regex, $row->text, $matches, PREG_SET_ORDER );

parse_str( $elm[2], $args );

$row->text = preg_replace($regex, $output, $row->text, 1);