php如何通过dom解析xml

创建一个book.xml文档，PHP通过DOM方式解析获得每本书的作者和书名

<?xml version="1.0" encoding="utf-8"?>

<bookshlf>

<bookid="book1">

<title>射雕英雄传</title>

<author>金庸</author>

</book>

<bookid="book2">

<title>红楼梦</title>

<author>曹雪芹</author>

</book>

<bookid="book3">

<title>西游记</title>

<author>罗贯中</author>

</book>

</bookshlf>

<?php

header("Content-Type:text/html;charset=utf-8");

$doc=new DOMDocument();

$doc->load("bookshlf.xml");

$books=$doc->getElementsByTagName("bookshlf");

$three=$books->item(0);

echo $three->nodeValue;

?>