var t= "";
setInterval(checkDb, 1000);
function checkDb(){
    <?php
        session_start();
            $servername = "localhost";
            $username = "user";
            $password = "password";
            $dbname = "RFID";
            // Create connection
            $conn = new mysqli($servername, $username, $password, $dbname);
                // Check connection
                if ($conn->connect_error) {
                     die("Connection failed: " . $conn->connect_error);
                }
                $sql = 'SELECT `id`, `rfid`, `dateandtime` FROM`scans`';
                    $result = $conn->query($sql);

                    if ($result->num_rows > 0) {

                    // output data of each row
                    while($row = $result->fetch_assoc()) {
                        $answer= "id: " . $row["id"]. " - RFID: " . $row["rfid"]. " - Date:" . $row["dateandtime"]. "<br>";
                    ?>

                    t= <?php echo json_encode($answer);?> + t ;
                    document.getElementById("myP").innerHTML = t;
                    <?php
                    }
                    } else {
                       echo "<br>" ."n0 resultsn";
                    }
                    $conn->close();
            session_destroy();?>
            t="";
        };