Encoding ampersands on the fly for site validation

//<?php
// Begin plugin code
$e = &$modx->event;

$id = $modx->event->params['id'];

if ($e->name == 'OnWebPagePrerender') {
	$o = &$modx->documentOutput; // get a reference of the output
	// Replace all ^text inside hats^ to <sup> tags, useful for more friendly Wayfinder replacements
	$o = preg_replace('%\^([()a-zA-Z0-9 ]*)\^%i', "<sup>$1</sup>",$o);
	// Replace orphan & with &
	$o = preg_replace('%&(?![a-zA-Z0-9#]{1,6})%i', "&",$o);
	// Replace ].]> with ]]>, useful for CDATA tags inside PHx calls: http://modxcms.com/forums/index.php?topic=31435.0
	$o = str_replace('/* ].]> */', '/* ]]> */',$o);
}

$e->output($o);
return '';

        if ($this->config['xhtml_urls']) {return preg_replace("/&(?!amp;)/","&", $host . $virtualDir . $url);}

$o = preg_replace('/&(?!amp;|#)/', "&",$o);