<br> tag for php

[aveon]

hey guys i have a php string

PHP Code:

$Data .= $glue.$User['username'];
$glue=","; 


this shows active users like

this aveon,paul,chris,so ans so

but i want it to be like

that
aveon
paul
chris

i need to put br somewhere but i really dnt kno also is it possible to post usernames with murkup??

also here is the full php code

PHP Code:

<?xml version="1.0" encoding="ISO-8859-1"?>

<plugins>
    <plugin active="1" product="vbulletin">
        <title>online_users</title>
        <hookname>global_start</hookname>
        <phpcode><![CDATA[$Data = "";       // Page Output Variable
$cache = array();

    // Collect Data
    $datecut      = TIMENOW - $vbulletin->options['cookietimeout'];
    $UsersOnline = $db->query("
        SELECT
            user.username, (user.options) AS invisible, user.usergroupid,
            session.userid,
            IF(displaygroupid=0, user.usergroupid, displaygroupid) AS displaygroupid
        FROM " . TABLE_PREFIX . "session AS session
        LEFT JOIN " . TABLE_PREFIX . "user AS user ON(user.userid = session.userid)
        WHERE session.lastactivity > $datecut and user.userid > 0
        " . iif($vbulletin->options['displayloggedin'] == 1, "ORDER BY username ASC") . "
    ");
$glue="";
        while($User = $db->fetch_array($UsersOnline) and strlen($Data)<80){
            if(!$cache[$User['userid']]){
            $cache[$User['userid']] = $User['userid'];

    $Data .= $glue.$User['username'];
$glue=",";
            }
        }
    $usersonline=$Data;
    unset($cache);]]></phpcode>
    </plugin>
</plugins>