Modifier une variable dans une session

$app=JFactory::getApplication();
		$app->setUserState('com_hikashop.shipping_address',$address_id);

function onBeforeOrderCreate(&$order, &$do){ 

 $app = JFactory::getApplication(); 
 $shipping_method = $app->getUserState('com_hikashop.shipping_data'); 

	if ($shipping_method[0]->id_relais!='0') //Mise en memoire de l'adresse et creation de l'adresse du relais
	{
		$user_id = hikashop_loadUser();//chargement de l'id du client
		$address_company=$shipping_method[0]->shipping_name;
		$address_street=$shipping_method[0]->adresse1;
		$address_street2=$shipping_method[0]->adresse2;
		$address_post_code=$shipping_method[0]->cp;
		$address_city=$shipping_method[0]->ville;
		$address_country=$shipping_method[0]->pays;
		$address_published='0';
		$address_default='0';

			
		$db =& JFactory::getDBO(); // enregistrement de l'adresse du relais dans la base de données
		$query = "INSERT INTO ".hikashop_table('address')." (address_user_id,address_company, address_street, address_street2, address_post_code, address_city, address_country, address_published, address_default)
		VALUES ('".$user_id."', '".$address_company."', '".$address_street."', '".$address_street2."', '".$address_post_code."', '".$address_city."', '".$address_country."', '0', '0' )";
		$db->setQuery( $query );
		$db->query();
		
		$db = JFactory::getDBO(); //Recuperation l'id de l'adresse du client qui vient d'etre enregistrer
		$db->setQuery('SELECT address_id FROM '.hikashop_table('address').' WHERE address_user_id = '.$user_id. ' ORDER BY address_id DESC LIMIT 1');
		$address_id = $db->loadResult(); 

		$app=JFactory::getApplication();//Rajout l'ID de l'adresse dans la session
		$app->setUserState('com_hikashop.shipping_address',$address_id); 

	}


$order->id_relais = $shipping_method[0]->id_relais; 
$order->adresse_relais = $shipping_method[0]->adresse_relais; 

}

$app->setUserState('com_hikashop.shipping_address',$address_id);

$order->order_shipping_address_id=$app->setUserState(HIKASHOP_COMPONENT.'.shipping_address',$address_id);