easyui Create Async Tree

client code:

<ul id="tt" class="easyui-tree"

url="tree2_getdata.php">
</ul>

server code:

4. $id = isset($_POST['id']) ? intval($_POST['id']) : 0;

5. include 'conn.php';
    
   $result = array();
   $rs = mysql_query("select * from nodes where parentId=$id");
   while($row = mysql_fetch_array($rs)){
       $node = array();
       $node['id'] = $row['id'];
       $node['text'] = $row['name'];
       $node['state'] = has_child($row['id']) ? 'closed' : 'open';
       array_push($result,$node);
   }
    
   echo json_encode($result);
    
   function has_child($id){
       $rs = mysql_query("select count(*) from nodes where parentId=$id");
       $row = mysql_fetch_array($rs);
       return $row[0] > 0 ? true : false;
   }