htmlpurifier/library/HTMLPurifier/Injector/DisplayLinkURI.php

<?php

/**
 * Injector that displays the URL of an anchor instead of linking to it, in addition to showing the text of the link.
 */
class HTMLPurifier_Injector_DisplayLinkURI extends HTMLPurifier_Injector
{

    public $name = 'DisplayLinkURI';
    public $needed = array('a');

    public function handleElement(&$token) {
    }

    public function handleEnd(&$token) {
        if (isset($token->start->attr['href'])){
            $url = $token->start->attr['href'];
            unset($token->start->attr['href']);
            $token = array($token, new HTMLPurifier_Token_Text(" ($url)"));
        } else {
            // nothing to display
        }
    }
}