php category, sub category tree

Question

I\'ve done this before in long complicated statements but I\'m trying to clean up some code.

I have the following table structures

parent_categories              


        

Answer 1

$qry = $conn->prepare('
  SELECT   a.pid, a.parent_name, b.category_name
  FROM     parent_categories a
      JOIN child_categories  b ON a.pid = b.lpid
  ORDER BY a.pid
');

if ($qry->execute()) {
  echo '
';

  $row = $qry->fetch();
  while ($row) {
    $current_pid = $row['pid'];

    echo '
', htmlentities($row['parent_name']), '
';
    do {
      echo '
', htmlentities($row['category_name']), '
';
    } while ($row = $qry->fetch() and $row['pid'] == $current_pid);
    echo '
';
  }

  echo '
';
}