<?php
/**
 * getAlias
 *
 * DESCRIPTION
 *
 * This snippet returns the alias of a page matching an id
 *
 * USAGE:
 *
 * [[!getAlias? &id=`[[+parent]]`]]
 */
 
$page = $modx->getObject('modResource', $id);
if(!empty($page)) {
    return $page->get('alias');
}
return '';
?>