DOMDocument replace occurrence of text in nodeValue with <a> link

function makeLinks($text) {
    $text = preg_replace('@(https?://([-\w\.]+[-\w])+(:\d+)?(/([\w/_\.#-]*(\?\S+)?[^\.\s])?)?)@', '<a href="$1" target="_blank">$1</a>', $text);
    $text = preg_replace('/@(\w+)/', '<a href="http://twitter.com/$1" target="_blank">@$1</a>', $text);
    $text = preg_replace('/\s#(\w+)/', ' <a href="http://search.twitter.com/search?q=%23$1" target="_blank">#$1</a>', $text);
    return $text;
}