Filter bad rss unhappy characters out

BadCharacterMungerFilter.php

<?php

class BadCharacterMungerFilter extends sfFilter
{
    public function execute($filterChain)
    {
        $filterChain->execute();
        // Execute this filter only once
        if ($this->isFirstCall()) {
            $response = $this->getContext()->getResponse();
            $content = $response->getContent();

            $bad_combos = array(
                html_entity_decode('&#x2013;', ENT_COMPAT, 'UTF-8') => '&#x2013;',
                html_entity_decode('&#8217;', ENT_COMPAT, 'UTF-8') => '&#2013;',
                html_entity_decode('&#8220;', ENT_COMPAT, 'UTF-8') => '&#8220;',
                html_entity_decode('&#8221;', ENT_COMPAT, 'UTF-8') => '&#8221;',
                chr(226) . chr(128) . chr(153) => '\'',
                chr(226) => '',
                chr(128) => '',
                chr(153) => '',
                '&acirc;' => '&#8217;',
            );

            $content = str_replace(array_keys($bad_combos), array_values($bad_combos), $content);

            $response->setContent($content);
        }

    }
}