<?php
class BinTree{
        public $data;
        public $left;
        public $right;
}
//前序遍历生成二叉树
function createBinTree(){
        $handle=fopen("php://stdin","r");
        $e=trim(fgets($handle));
        if($e=="#"){
                $binTree=null;
        }else{
                $binTree=new BinTree();
                $binTree->data=$e;
                $binTree->left=createBinTree();
                $binTree->right=createBinTree();
        }   
        return $binTree;
}    

$tree=createBinTree();

var_dump($tree);

A
B
#
D
#
#
C
#
#
object(BinTree)#1 (3) {
  ["data"]=>
  string(1) "A"
  ["left"]=>
  object(BinTree)#2 (3) {
    ["data"]=>
    string(1) "B"
    ["left"]=>
    NULL
    ["right"]=>
    object(BinTree)#3 (3) {
      ["data"]=>
      string(1) "D"
      ["left"]=>
      NULL
      ["right"]=>
      NULL
    }
  }
  ["right"]=>
  object(BinTree)#4 (3) {
    ["data"]=>
    string(1) "C"
    ["left"]=>
    NULL
    ["right"]=>
    NULL
  }
}