php-递归函数类别数据库

我希望创建一个我还没有想法的递归函数

这是我的代码以从数据库中获取类别

  <?PHP
  $sql = MysqL_query("SELECT * FROM categories WHERE category_parent = '1' ORDER BY lft ASC");
  while($row = MysqL_fetch_array($sql)) {
  echo "<li><a href='/{$row['category_safe_name']}/'>{$row['category_name']}</a>";
  $sql2 = MysqL_query("SELECT * FROM categories WHERE category_parent = '{$row['category_id']}'");
  if(MysqL_num_rows($sql2) > 0)
  echo "<ul>";
  while($row2 = MysqL_fetch_array($sql2)) {
  echo "<li><a href='/{$row2['category_safe_name']}/'>{$row2['category_name']}</a><li>";
  }
  if(MysqL_num_rows($sql2) > 0)
  echo "</ul>";
  echo "</li>";
  }
  ?>

目前看起来像

Top Category (category_id = 1)
   Category
       Sub Category

我的代码适用于类别&子类别.我打算做的是使我的代码支持无限的子类别

欢迎任何帮助和建议.

谢谢

解决方法:

我会做 ：

<?PHP
function getChildren($id=1) {
  $sql = MysqL_query("SELECT * FROM categories WHERE category_parent = '$id' ORDER BY lft ASC");
  echo "<ul>";
  while($row = MysqL_fetch_array($sql)) {
    echo "<li><a href='/{$row['category_safe_name']}/'>{$row['category_name']}</a>";
    getChildren($row['category_id']);
    echo "</li>";
  }
  echo "</ul>";
}

getChildren();
?>