HasSubtree(treeA,treeB)

    if(treeA->val==treeB->val)//根结点相同

        res=tree1HasTreeB(treeA.treeB)

    if !res

        res=HasSubtree(treeA->left.treeB)//第一层遍历

    if !res

        res=HasSubtree(treeA->right.treeB)//第一层遍历

    return res

tree1HasTreeB(treeA,treeB)

    //顺序不能变

    if treeB==null  //B到底的时候，就是true

        return true

    if treeA==null

        return false//B没到底，A到底了，就是false

    if treeA->val!=treeB->val //A和B的结点没对上

        return false

    //短路语法 ，如果前面的是false，直接返回false,后面不用走

    return tree1HasTreeB(treeA->left,treeB->left)&&tree1HasTreeB(treeA->right,treeB->right)

<?php

class TreeNode{

    public $val;

    public $left = NULL;

    public $right = NULL;

    public function __construct($val){

        $this->val = $val;

    }  

}

//构造两棵树

$node1=new TreeNode(1);

$node2=new TreeNode(2);

$node3=new TreeNode(3);

$node4=new TreeNode(4);

$node5=new TreeNode(5);

$treeA=$node1;

$node1->left=$node2;

$node1->right=$node3;

$node3->left=$node4;

$node3->right=$node5;

//var_dump($treeA);

$node6=new TreeNode(3);

$node7=new TreeNode(4);

$node6->left=$node7;

$treeB=$node6;

//var_dump($treeB);

function HasSubtree($pRoot1,$pRoot2){

        $res=false;

        if($pRoot1==null || $pRoot2==null) return $res;

        if($pRoot1->val==$pRoot2->val) $res=tree1HasTree2($pRoot1,$pRoot2);

        if(!$res) $res=HasSubtree($pRoot1->left,$pRoot2);

        if(!$res) $res=HasSubtree($pRoot1->right,$pRoot2);

        return $res;

}

function tree1HasTree2($treeA,$treeB){

        if($treeB==null) return true;

        if($treeA==null) return false;

        if($treeA->val!=$treeB->val) return false;

        return tree1HasTree2($treeA->left,$treeB->left)&&tree1HasTree2($treeA->right,$treeB->right);

}

var_dump(HasSubtree($treeA,$treeB));