function execute($par)
 {
     global $wgRequest, $wgOut, $wgUser;
     $this->setHeaders();
     # Get request data from, e.g.
     $pageId = $wgRequest->getText('pageId');
     $revId = $wgRequest->getText('revId');
     $receiver = $wgRequest->getText('receiver');
     if (!$pageId || !$revId || !$receiver) {
         $output = '<span class="error">' . htmlspecialchars(wfMsg('notificator-special-page-accessed-directly')) . '</span>';
     } else {
         $titleObj = Title::newFromID($pageId);
         $pageTitle = $titleObj->getFullText();
         $linkToPage = $titleObj->getFullURL();
         if (!Notificator::receiverIsValid($receiver)) {
             $output = '<span class="error">' . htmlspecialchars(wfMsg('notificator-e-mail-address-invalid') . ' ' . wfMsg('notificator-notification-not-sent')) . '</span>';
             $output .= Notificator::getReturnToText($linkToPage, $pageTitle);
             $wgOut->addHTML($output);
             return;
         }
         $oldRevId = Notificator::getLastNotifiedRevId($pageId, $revId, $receiver);
         if ($oldRevId >= 0) {
             if ($oldRevId > 0) {
                 // Receiver has been notified before - send the diff to the last notified revision
                 $mailSubjectPrefix = '[' . htmlspecialchars(wfMsg('notificator-change-tag')) . '] ';
                 $wgOut->addModules('mediawiki.action.history.diff');
                 $diff = Notificator::getNotificationDiffHtml($oldRevId, $revId);
                 $notificationText = wfMsg('notificator-notification-text-changes', htmlspecialchars($wgUser->getName()), Html::element('a', array('href' => $linkToPage), $pageTitle)) . Html::rawElement('div', array('style' => 'margin-top: 1em'), $diff);
             } else {
                 // Receiver has never been notified about this page - so don't send a diff, just the link
                 $mailSubjectPrefix = '[' . htmlspecialchars(wfMsg('notificator-new-tag')) . '] ';
                 $notificationText = wfMsg('notificator-notification-text-new', htmlspecialchars($wgUser->getName()), Html::element('a', array('href' => $linkToPage), $pageTitle));
             }
             $mailSubject = htmlspecialchars($mailSubjectPrefix . $pageTitle);
             if (Notificator::sendNotificationMail($receiver, $mailSubject, $notificationText)) {
                 $output = '<strong>' . htmlspecialchars(wfMsg('notificator-following-e-mail-sent-to', $receiver)) . '</strong><div style="margin-top: 1em;"><h3>' . wfMsg('notificator-subject') . ' ' . $mailSubject . '</h3><p>' . $notificationText . '</p></div>';
                 Notificator::recordNotificationInDatabase($pageId, $revId, $receiver);
             } else {
                 $output = '<span class="error">' . htmlspecialchars(wfMsg('notificator-error-sending-e-mail', $receiver)) . '</span>';
             }
         } elseif ($oldRevId == -1) {
             $output = '<span class="error">' . htmlspecialchars(wfMsg('notificator-error-parameter-missing')) . '</span>';
         } elseif ($oldRevId == -2) {
             $output = '<strong>' . htmlspecialchars(wfMsg('notificator-notified-already', $receiver) . ' ' . wfMsg('notificator-notification-not-sent')) . '</strong>';
         }
         $output .= Notificator::getReturnToText($linkToPage, $pageTitle);
     }
     $wgOut->addHTML($output);
 }