php - Craft calculator loop -

i'm trying craft calculator game.

i have database looks :

crafts :

id    item_id   item_name    amount  3     1895                  5  8     2486         c          1 

craft_materials :

id    craft_id   item_id    item_name   amount  1       3        2486          c         15  2       3        5302          d         23  3       3        5698          e          2  4       8        2014          f          3 

and here query retrieve data :

$craftproduct = $db->query("select * crafts item_id=$item"); $craftproduct->setfetchmode(pdo::fetch_obj); $product = $craftproduct->fetch();  $craftid = $product->id;  $craftmaterial = $db->query("select * craft_materials craft_id=$craftid"); $craftmaterial->setfetchmode(pdo::fetch_obj);  echo '<ul>';     echo '<li>'.$product->item_name.' ('.$product->amount.')</li>';         echo '<ul>';         while($material = $craftmaterial->fetch()){              echo '<li>'.$material->item_name.' ('.$material->amount.')</li>';         }         echo '</ul>'; echo '</ul>'; 

what want take material id , check if corresponds craft. if does, want show material needed craft it.

i want looks :

- (5)     - c (15)         - f (3)     - d (23)     - e (2) 

however, don't know how loop. can me?

here basic recursion setup:

function render_item($item_id) {     $product = fetch_item($item_id);    // select crafts item_id = $item_id     $children = "";     foreach (fetch_children($product->id) $child_id) { // select craft_mats craft_id = $product->id         $children .= render_item($child_id);     }     echo "<li>" . $product->item_name . "<ul>" . $children . "</ul></li>"; }  echo "<ul>" . render_item(1895) . "</ul>"