<a href="<?php echo $clang == 'en' ? "http://www.website.com/english/" : "http://www.website.com/news/"; ?>" class="xyz_<?php echo $clang; ?>" onClick="_gaq.push(['_trackEvent', 'banner', 'click', 'News Button']);">News Button</a>
That would be the quick way to add it. Let me know if you need anything clarified. I condensed your php to be handled by a ternary operator. No need for that if statement the way it was.