chat php

<?php

session_start();

$_SESSION["latest_view_id"] = (isset($_SESSION["latest_view_id"])) ? $_SESSION["latest_view_id"] : 0;

$db = new PDO("mysql:host=localhost;dbname=pokemon-trash", "root", "");

$req = $db->query("SELECT * FROM messages_chat WHERE id > ".$_SESSION["latest_view_id"]);
while($msg = $req->fetch()) {
    //// affichage des messages

    $_SESSION["latest_view_id"] = $msg["id"];
}
$req->closeCursor();

?>