Prestashop SAV Client et message sur commande

public static function getMessagesByOrderId($id_order, $private = false, Context $context = null)
{
if (!Validate::isBool($private))
die(Tools::displayError());
if (!$context)
$context = Context::getContext();
$m = Db::getInstance()->executeS('
SELECT m.*, c.`firstname` AS cfirstname, c.`lastname` AS clastname, e.`firstname` AS efirstname, e.`lastname` AS elastname,
(COUNT(mr.id_message) = 0 AND m.id_customer != 0) AS is_new_for_me
FROM `'._DB_PREFIX_.'message` m
LEFT JOIN `'._DB_PREFIX_.'customer` c ON m.`id_customer` = c.`id_customer`
LEFT JOIN `'._DB_PREFIX_.'message_readed` mr
ON mr.`id_message` = m.`id_message`
AND mr.`id_employee` = '.(isset($context->employee) ? (int)$context->employee->id : '\'\'').'
LEFT OUTER JOIN `'._DB_PREFIX_.'employee` e ON e.`id_employee` = m.`id_employee`
WHERE m.`id_order` = '.(int)$id_order.'
'.(!$private ? ' AND m.`private` = 0' : '').'
GROUP BY m.id_message
ORDER BY m.date_add desc
');

$o = Db::getInstance()->executeS('
SELECT ct.*, m.*, c.`firstname` AS cfirstname, c.`lastname` AS clastname, e.`firstname` AS efirstname, e.`lastname` AS elastname
FROM `'._DB_PREFIX_.'customer_thread` ct
LEFT JOIN `'._DB_PREFIX_.'customer_message` m ON m.`id_customer_thread` = ct.`id_customer_thread`
LEFT JOIN `'._DB_PREFIX_.'customer` c ON ct.`id_customer` = c.`id_customer`
LEFT OUTER JOIN `'._DB_PREFIX_.'employee` e ON e.`id_employee` = m.`id_employee`
WHERE ct.`id_order` = '.(int)$id_order.'
ORDER BY m.date_add desc
');

function tri($a, $b){
$ad = strtotime($a['date_add']);
$bd = strtotime($b['date_add']);
return ($bd-$ad);
}

$arr = array_merge($o,$m);
usort($arr, 'tri');
return $arr;
}