全部家当　求树型无限分类的调用　高手来啊

要写递归,给你个简单的实例吧:
function tree($_id=null){
   $sql = "select * from tree where pid = $_id";
   //这里执行查询
  $s = "";
   while(判断查询结果是否结束,并移动数据库指针){
     $s .= $r["id"] . $r["title"] . $this->tree($r["id"]);
   }
   return $s;
}