košík - kde mám chybu?

        <a href="kosik.php">
        <div class="kosik">
          <?php
            require('kosik_update.php');
            $celkovacena=0;
            foreach($_SESSION["polozky_kosiku"] as $polozka_kosiku)
              {
              echo $celkovacena=($polozka_kosiku['cena']*$polozka_kosiku['kusy']).',- Kč';
              }
          ?>  
        </div>
        </a>

                <form method="post" action="kosik_update.php">
                <input type="number" name="kusy" class="ks" min="1" max="100" value="1">ks
                <input type="hidden" name="id" value="'.$obsah['id'].'">
                <input type="hidden" name="typ" value="pridat">
                <input type="hidden" name="vratitadresu" value="'.$aktualni_adresa.'">
                <input type="submit" class="koupit" value="Koupit">
                </form>

<?php
require('databaze/pripojeni.php');
session_start();
if(isset($_POST["typ"]) && $_POST["typ"]=='pridat' && $_POST["kusy"]>0)
    {
    $udaj=$pripoj->prepare('SELECT * FROM produkty WHERE id="'.$_POST['id'].'" LIMIT 1');
    $udaj->bind_param('s', $nova_polozka['id']);
    $udaj->execute();
    $udaj->bind_result($nazev, $cena);
    while($udaj->fetch())
      {
      $nova_polozka['nazev']=$nazev;
      $nova_polozka['cena']=$cena;
      $nova_polozka['kusy']=$_POST["kusy"];
      
      if(isset($_SESSION["polozky_kosiku"]))
        {
          if(isset($_SESSION["polozky_kosiku"][$nova_polozka['id']]))
            {
            unset($_SESSION["polozky_kosiku"][$nova_polozka['id']]);
            }
        }
      }
      $_SESSION["polozky_kosiku"][$nova_polozka['id']]=$nova_polozka;  
    } 

$vratitadresu = (isset($_POST["vratitadresu"]))?urldecode($_POST["vratitadresu"]):'';
header('Location:'.$vratitadresu);
?

<form method="post" action="kosik_update.php">
<table>
  <tr><th>Nazev</th></tr>
  <?php
    if(isset($_SESSION["polozky_kosiku"]))
      {
        $celkovacena = 0;
        foreach ($_SESSION['polozky_kosiku'] as $polozka_kosiku)
        {
            $nazev = $polozka_kosiku["nazev"];
            echo '<tr>';
            echo '<td>'.$nazev.'</td>';
            echo '</tr>';
        }
      }
  ?>
</table>
</form>

    $query = "SELECT nazev, cena, obrazek FROM produkty WHERE id={$id}";
    $stmt = $pripoj->prepare($query);
    $stmt->execute();
    while ($row=$stmt->fetch()){
        $nazev = $row['nazev'];
        $cena = $row['cena'];
        $obrazek = $row['obrazek'];
    }

$new_product['id'] = $_POST['id'];
$statement->bind_param('i', $new_product['id']);

Fatal error: Call to a member function bind_param() on a non-object

<?php
session_start();
require('databaze/pripojeni.php');
$vysledek=mysqli_query($pripoj, 'select * from produkty where id='.$_POST['id']);
$produkt=mysqli_fetch_array($vysledek);
if(isset($_POST["typ"]) && $_POST["typ"]=='pridat')
  {
  $polozka['id']=$produkt['id'];
  $polozka['nazev']=$produkt['nazev'];
  $polozka['cena']=$produkt['cena'];
  $polozka['mnozstvi']=$_POST['mnozstvi'];
  $_SESSION['kosik'][]=$polozka;
  }
?>
<table border="1">
  <tr>
    <th>id</th>
    <th>nazev</th>
    <th>cena</th>
    <th>mnozstvi</th>
  </tr>
<?php
foreach ($_SESSION['kosik'] as $kosik)
  {
  echo '<tr>
          <td>'.$kosik['id'].'</td>
          <td>'.$kosik['nazev'].'</td>
          <td>'.$kosik['cena'].'</td>
          <td>'.$kosik['mnozstvi'].'</td>
       </tr>';
  }
?>
</table>