目录tree在页面上显示

//完整的目录结构    function get_dir_tree($uid,$from_dir=0){        $sql = "select dir_id,dir_name,depth,p_id from $this->_dir_table where user_id=$uid and is_del=0 and dir_id>=$from_dir";        $res = $this->db->query($sql)->result_array();        if(!isset($res[0])){            return null;        }        $this->load->helper('array');        //获取depth区间        $max_depth = 0;        foreach($res as $dps => $d){            if($d['depth']>$max_depth){                $max_depth = $d['depth'];            }        }        for($i=$max_depth;$i>=0;$i--){ //处理成树形，子集存在child里,有没有自己看有没有child字段            foreach($res as $key=>$val){                if($val['depth']==$i){                    foreach($res as $k=>$v){                        if($val['p_id']==$v['dir_id']){                            $v['child'][] = $val;                            $res[$k] = $v;                            unset($res[$key]);                        }                    }                }            }        }        $return =  $this->has_child_then_add_ul($res);        $html="
                        
全部文件
";        $html.=$return."
";        return $html;    }    private function has_child_then_add_ul($res,$html='',$collaps_times=1){        $collaps = 15;//前端写的是m_l_15, m_l_30 这样的 , 15为一个单位，跟前端商定就好        $indent = $collaps_times*$collaps;        $has_sibling = 0;        $ul_begin = "
";        $ul_end = "
";        $li_begin = "
%s
";//%s处是dir_name        // $li_begin = "
%s";//%s处是dir_name        $li_end = "
";        $count_li_end = $count_ul_end = 0;        foreach($res as $key=>$val){            if(0==$key){                $html.=$ul_begin;            }            $html.=sprintf($li_begin,$indent,$val['dir_name']);            $count_li_end++;            if(isset($val['child'])){                $html = $this->has_child_then_add_ul($val['child'],$html,$collaps_times+1);            }            $html.=$li_end;            if(!isset($res[$key+1])){                $html.=$ul_end;            }        }        return $html ;    }