<?xml version="1.0" encoding="utf-8"?>
<root>
 <book id="1">
  <title>title1</title>
 </book>
 <book id="2">
  <title>title2</title>
 </book>
 <book id="3">
  <title>title3</title>
 </book>
 <book id="4">
  <title>title4</title>
 </book>
 <book id="5">
  <title>title5</title>
 </book>
</root>

<?php $doc = new DOMDocument(); $doc->load('example.xml'); $books = $doc -> getElementsByTagName("book"); //遍历 foreach ($books as $book) { echo $book->getAttribute('id')."-"; echo $book->getElementsByTagName("title")->item(0)->nodeValue; echo "<br>"; }

1-title1 
2-title2 
3-title3 
4-title4 
5-title5

<?php

 $doc = new DOMDocument();
 $doc->load('example.xml');

 $books = $doc -> getElementsByTagName("book");
 //遍历
 foreach ($books as $book) {
  //将id=3的title设置为33333
  if($book->getAttribute('id')==3){
   echo $book->getAttribute('id')."-";
   echo $book->getElementsByTagName("title")->item(0)->nodeValue="33333";
   echo "<br>";
  }
 }
 //对文件做修改后，一定要记得重新sava一下，才能修改掉原文件
 $doc -> save('example.xml');

<?xml version="1.0" encoding="utf-8"?>
<root>
 <book id="1">
  <title>title1</title>
 </book>
 <book id="2">
  <title>title2</title>
 </book>
 <book id="3">
  <title>33333</title>
 </book>
 <book id="4">
  <title>title4</title>
 </book>
 <book id="5">
  <title>title5</title>
 </book>
</root>

<?php

 $doc = new DOMDocument();
 $doc->load('example.xml');

 $root = $doc -> documentElement;//根标签 
 $books = $doc -> getElementsByTagName("book");
 //遍历
 foreach ($books as $book) {
  //将id=4的删除
  if($book->getAttribute('id')==4){
   $root->removeChild($book);
  }
 }
 //对文件做修改后，一定要记得重新sava一下，才能修改掉原文件
 $doc -> save('example.xml');

<?xml version="1.0" encoding="utf-8"?>
<root>
 <book id="1">
  <title>title1</title>
 </book>
 <book id="2">
  <title>title2</title>
 </book>
 <book id="3">
  <title>33333</title>
 </book>

 <book id="5">
  <title>title5</title>
 </book>
</root>