Присвоить class="" для сылок вложений в зависимости от типа вложения - Модификации K2

<a href="/announcements/item/download/1_d9abbb66014e7ffe4b629aea4f952bad.html" title="Download-file1">Download-file1.pdf</a>
<a href="/announcements/item/download/3_74b69ecd8bcaf2c6ec13b3c746c92c72.html" title="track_07">track_07.mp3</a>

<a class="classPdf" href="/media/k2/attachments/download-file1.pdf" title="Download-file1">Download-file1.pdf</a>
<a class="classMp3" href="/media/k2/attachments/track_07.mp3" title="track_07.mp3">track_07.mp3</a>

<?php 
$link = '<a href="/announcements/item/download/3_74b69ecd8bcaf2c6ec13b3c746c92c72.html" title="track_07">track_07.mp3</a>';
$class = preg_filter('/<a[^<>]+?>.*\.(.*)<\/a>/uis', '<?php 
$link = '<a href="/announcements/item/download/3_74b69ecd8bcaf2c6ec13b3c746c92c72.html" title="track_07">track_07.mp3</a>';
$class = preg_filter('/<a[^<>]+?>.*\.(.*)<\/a>/uis', '$1', $link);
echo ($class ? str_replace('<a','<a class ="class'.$class.'" ', $link ):$link);
?>', $link);
echo ($class ? str_replace('<a','<a class ="class'.$class.'" ', $link ):$link);
?>