Дмитрий Рекун

$id_s = implode(',', $arr);
$query = $db->getQuery(true);
$query->select(
	$db->quoteName(
		array('vv.virtuemart_user_id', 'vv.customer_number',  'vu.last_name', 'vu.first_name', 'vu.city', 'vu.school', 'vu.class', 'vu.teacher')
	)
);
$query->from($db->quoteName('#__virtuemart_vmusers', 'vv'));
$query->leftJoin($db->quoteName('#__virtuemart_userinfos', 'vu')) ' ON ' . $db->quoteName('vv.virtuemart_user_id') . ' = ' . $db->quoteName('vu.virtuemart_user_id'));
$query->where($db->quoteName('vv.virtuemart_user_id') . ' IN(' . $id_s . ')');
$db->setQuery($query);