Show mysql results regardless of shopping cart

I am creating a shopping cart system, which works very well, now the problem comes where it shows the results of the cart ( cesta.php), I want to show results regardless of what the user has inserted in the cart, to make it easier if they want to buy more products.

Let's say if we add 3 products to buy, with id1, id2, id3.

And in the Database ( productos) there are 6 records.

Well, it should show id4, id5, id6, since as I mentioned before, the user has already entered to buy the id1, id2, id3.

I save the shopping cart in a session as follows:

I create the shopping cart on the pagecard.php

 //Carro de la compra

//Si esta definida la ID obtenido por URL
if (isset($_GET['articulo'])) {

    $id_tutorial = $_GET['articulo'];//Obtenemos el ID del tutorial añadido, para poder acer comprobaciones a mostrar otros resultados.

    //Si esta definido la sesion carro -> es decir si ay algun articulo comprado
    if (isset($_SESSION['carrito'])) {

        $arreglo = $_SESSION['carrito'];
        $encontro = false;      

        for ($i=0; $i<count($arreglo); $i++) { 

            if ($arreglo[$i]['Id'] == $_GET['articulo']) {
                $encontro = true;               
            }
        }

        if ($encontro == false) {


            $titulo = "";
            $precio = 0;
            $precioUSD = 0;
            $icon = "";

            $stmt = $c->prepare("SELECT titulo,precio,icon,id_autor FROM tutoriales WHERE page=? and status=1");
            $stmt->bind_param("i",$_GET['articulo']);
            $stmt->execute();
            $stmt->store_result();
            if ($stmt->num_rows > 0) {
                $stmt->bind_result($titulo,$precio,$icon,$id_autor);
                while ($stmt->fetch()) {

                    //Sentencia prepare -> autor proyecto
                    $stmtN = $c->prepare("SELECT autor FROM autor WHERE id_autor=?");           
                    $stmtN->bind_param("i", $id_autor);         
                    $stmtN->execute();          
                    $stmtN->bind_result($autor);            
                    $stmtN->fetch();            
                    $stmtN->close();

                    $datosnuevos = array('Id' => $_GET['articulo'], 'Titulo' => $titulo, 'Precio' => $precio, 'Icon' => $icon, 'Cantidad' => 1 );

                    /*
                        #Si se utiliza array_push() para añadir un solo elemento al array, es mejor utilizar $array[] = ya que de esta forma no existe la sobrecarga de llamar a una función. 
                    */

                    //array_push($arreglo, $datosnuevos); 
                    $arreglo[] = $datosnuevos;
                    $_SESSION['carrito'] = $arreglo;

                    $data = $_SESSION['carrito'];
                    $value_carrito = count($data);
                    $_SESSION['compras'] = $value_carrito;

                } $stmt->close();


            } else {
                $stmt->close();
            }
        }   

    } else { //Caso falso añadimos primer articulo al carro

        $titulo = "";
        $precio = 0;
        $precioUSD = 0;
        $icon = "";

        $stmt = $c->prepare("SELECT titulo,precio,icon,id_autor FROM tutoriales WHERE page=? and status=1");
        $stmt->bind_param("i",$_GET['articulo']);
        $stmt->execute();
        $stmt->store_result();
        if ($stmt->num_rows > 0) {
            $stmt->bind_result($titulo,$precio,$icon,$id_autor);
            while ($stmt->fetch()) {

                //Sentencia prepare -> autor proyecto
                $stmtN = $c->prepare("SELECT autor FROM autor WHERE id_autor=?");           
                $stmtN->bind_param("i", $id_autor);         
                $stmtN->execute();          
                $stmtN->bind_result($autor);            
                $stmtN->fetch();            
                $stmtN->close();

            } $stmt->close();

        } else {
            $stmt->close();
        }       

            $arreglo[] = array('Id' => $_GET['articulo'], 'Titulo' => $titulo, 'Precio' => $precio, 'Icon' => $icon, 'Cantidad' => 1 );

            $_SESSION['carrito'] = $arreglo;

            $data = $_SESSION['carrito'];
            $value_carrito = count($data);
            $_SESSION['compras'] = $value_carrito;

            //echo "<script>window.location.reload();</script>";


    }

}