$query = 'SELECT guest, usertype, client_id' .
 ' FROM #__session' .
 ' WHERE client_id = 0';

$datenow = date("Y-m-d H:i:s");
$time_string = strtotime($datenow);
// Modificacion consulta para visualizar usuarios activos en los ult. 10  minutos
$extra_time = 600; //ejemplo: 10 min x 60 seg
$online_time = ($time_string-$extra_time);

$query = "SELECT a.guest, a.usertype, a.client_id"
 ."\n FROM #__session AS a"
 ."\n WHERE a.client_id=0 AND a.time>'$online_time'";

$query = 'SELECT DISTINCT a.username' .

 ' FROM #__session AS a' .
 ' WHERE client_id = 0' .
 ' AND a.guest = 0';

$datenow = date("Y-m-d H:i:s");
$time_string = strtotime($datenow);
// Modificacion consulta para visulizar usuarios activos en los ult. 10 minutos
$extra_time = 600; //10 min x 60 seg
$online_time = ($time_string-$extra_time);

// Nueva Consulta para mostrar solo usuarios activos en los ult. 10 minutos
$query = "SELECT DISTINCT a.username, a.userid, u.name"
 ."\n FROM #__session AS a, #__users AS u"
 ."\n WHERE (a.userid=u.id) AND (a.guest = 0) AND (NOT ( a.usertype is NULL OR a.usertype = '' )) AND a.time>'$online_time'"
 ."\n ORDER BY ".(($ueConfig['name_format'] > 2) ? "a.username" : "u.name")." ASC";