php 将一个二维数组转换成有父子关系的数组

leaf(0);
 *   $nav=$tree->navi(15);
 
     = 
      __construct(,  = ('id', 'pid'),  = 0->result = ->fields = ->root = ->
      (->result  [[->fields[1]]][] = ( ( = ();  > 0; -- (   =>  (!(, -> (!->->tmp = (, ->already[] =  (   =>  ([->fields[0]] == ->tmp[0[][]['child'] = ->tmp[1->tmp = (, [->tmp = ->tmp = 
      recur_n(,  (   ([->fields[0]] == ->arr[] =  ([->fields[1]] != ->root) ->recur_n(, [->fields[1
      recur_p( (  ->arr[] = [->fields[0 (['child']) ->recur_p(['child'
      leaf( =  = ( == ) ? ->root :  ->tmp[
      navi(->arr = ->recur_n(->result, (-> ->
      leafid(->arr = ->arr[] = ->recur_p(->leaf( ->?>