Duplicate results from mysql

I'm new to php, but I have already made some query's for my webshop. I have a little problem now with making the invoice. I'm trying put the invoice data from the database in a table in my website, but it duplicates itself.

Product_id | Product name | amount | price | subtotal|
2            kippensoep     1         €3      €3
2            kippensoep     1         €3      €3
2            kippensoep     1         €3      €3
4            Loempia's      1        €10     €10
4            Loempia's      1        €10     €10
4            Loempia's      1        €10     €10
4            Loempia's      1        €10     €10

So as you can see, the product_id , product_names are duplicated. It's strange because in the database it isn't duplicated. Here's the php code.

<?php
  $maxfac1 = mysql_fetch_array(mysql_query("SELECT MAX(transactie.factuur_id) FROM transactie , account WHERE transactie.id = $session_user_id"));

  unset ($maxfac1[0]); 
  $maxfactuur_id = implode (" ",$maxfac1);

  $productinfo = mysql_query("SELECT * FROM producten, transactie, factuur WHERE producten.product_id = factuur.product_id AND factuur.factuur_id = $maxfactuur_id AND factuur.gebruikers_id= $session_user_id");

  $totaal=0;
  $subtotaal=0;

  while ($row = mysql_fetch_array($productinfo))
  {
  ?>
  <tr>
    <td><?php echo $row['product_id']?></td>
    <td><?php echo $row['name'] ?></td>
    <td><?php echo $row['amount'] ?></td>
    <td>€<?php echo $row['price'] ?></td>
    <?php $subtotaal = ($row['price']*$row['amount']);?>
    <td>€<?php echo "$subtotaal" ;$totaal+= $subtotaal;?></td>
  </tr>

  <?php
  }
  ?>
?>

I hope you guys can help me and find a solution.

EDIT session_user_id checks if the user is logged in. Then it returns the id from the user who is logged in.

Try to check rows are unique. And add GROUP BY producten.product_id to your query.