用PHP5的SimpleXML解析XML文档

messages.xml
========================================================
<?xml version="1.0" ?>
<!--Sample XML document -->
<SystemMessage>
　　 　 <MessageTitle>System Down for Maintenance</MessageTitle>
　　　　<MessageBody>Going down for maintenance soon!</MessageBody>
　　　　<MessageAuthor>
　　 <MessageAuthorName>Joe SystemGod</MessageAuthorName>
　　 <MessageAuthorEmail>systemgod@someserver.com</MessageAuthorEmail>
　　　　</MessageAuthor>
　　　　<MessageDate>March 4, 2004</MessageDate>
　　 <MessageNumber>10</MessageNumber>
</SystemMessage>

========================================================

xml 是一种创建元数据的语言,元数据是描述其它数据的数据,PHP中的XML处理是基于LIBXML2的，安装时默认开启。

可以通过phpinfo()函数查看是否开启了XML处理模块,DOM,LIBXML,SAMPLEXML。

首先,通过samplexml_load_file函数把xml文件加载到一个对象中,samplexml_load_file可以用户远程文件.
例如:

$xml = samplexml_load_file("messages.xml"); // 本地文件,当前目录
$xml = samplexml_load_file("http://www.xml.org.cn/messages.xml"); // 远程web服务器

用 var_dump($xml) 和 print_r($xml) 分别输出其结构.var_dump给出了变量的类型和长度,而print_r可读性更强
输出对象中的所有元素名称和它的值.

echo $xml->MessageTitle;　//输出消息的标题
echo $xml->MessageBody; // 输出消息体
echo $xml->MessageAuthor;　//消息的作者

echo $xml->MessageDate;　　// 消息产生的日期

echo $xml->MessageNumber;　　// 消息代码

===================================================
另外,还有一个函数,可以把XML字符串加载到一个simplexml对象中取

$channel =<<<_XML_
<channel>
<title>What's For Dinner</title>
<link>http://menu.example.com/</link>
<description>These are your choices of what to eat tonight. </description>
</channel>
_XML_;

$xml = simplexml_load_string($channel);
===================================================

rss.xml

=============================================
<?xml version="1.0" encoding="utf-8"?>
<rss version="0.91">
<channel>
　<title>What's For Dinner</title>
　<link>http://menu.example.com/</link>
　<description>These are your choices of what to eat tonight.</description>
　<item>
　 <title>Braised Sea Cucumber</title>
　 <link>http://menu.example.com/dishes.php?dish=cuke</link>
　 <description>Gentle flavors of the sea that nourish and refresh you. </description>
　</item>
　<item>
　 <title>Baked Giblets with Salt</title>
　 <link>http://menu.example.com/dishes.php?dish=giblets</link>
　 <description>Rich giblet flavor infused with salt and spice. </description>
　</item>
　<item>
　 <title>Abalone with Marrow and Duck Feet</title>
　 <link>http://menu.example.com/dishes.php?dish=abalone</link>
　 <description>There's no mistaking the special pleasure of abalone. </description>
　</item>
</channel>
</rss>
=====================================================

1.访问具有相同元素名称的节点

2.通过foreach循环所有相同元素名称的子节点

foreach($xml->channel->item as $key=>$value)
{
print "Title: " . $item->title . "/n";
}

3.输出整个文档

echo $xml->asXML();

4.把节点作为字符串输出
echo $xml->channel->item[0]->asXML();

这将输出文本

<item>
<title>Braised Sea Cucumber</title>
<link>http://menu.example.com/dishes.php?dish=cuke</link>
<description>Gentle flavors of the sea that nourish and refresh you. </description>
</item>

带文件名参数的asXML将会把原本输出的内容保存为一个文件

$xml->channel->item[0]->asXML("item[0].xml");

完整的代码:

rss.xml
=====
<?xml version="1.0" encoding="utf-8"?>
<rss version="0.91">
<channel>
　<title>What's For Dinner</title>
　<link>http://menu.example.com/</link>
　<description>These are your choices of what to eat tonight.</description>
　<item>
　 <title>Braised Sea Cucumber</title>
　 <link>http://menu.example.com/dishes.php?dish=cuke</link>
　 <description>Gentle flavors of the sea that nourish and refresh you. </description>
　</item>
　<item>
　 <title>Baked Giblets with Salt</title>
　 <link>http://menu.example.com/dishes.php?dish=giblets</link>
　 <description>Rich giblet flavor infused with salt and spice. </description>
　</item>
　<item>
　 <title>Abalone with Marrow and Duck Feet</title>
　 <link>http://menu.example.com/dishes.php?dish=abalone</link>
　 <description>There's no mistaking the special pleasure of abalone. </description>
　</item>
</channel>
</rss>

rss.php
======
<?php
$xml = simplexml_load_file("rss.xml");

echo "<h3>".$xml->channel->title."</h3><br>";
echo "<ul>";
echo "<li>Title:".$xml->channel->item[0]->title."</li>";
echo "<li>Title:".$xml->channel->item[1]->title."</li>";
echo "<li>Title:".$xml->channel->item[2]->title."</li>";
echo "</ul>";
print "Title: " . $xml->channel->item[0]->title . "/n<br>";
print "Title: " . $xml->channel->item[1]->title . "/n<br>";
print "Title: " . $xml->channel->item[2]->title . "/n<br>";
echo "<hr>";

foreach ($xml->channel->item[0] as $element_name => $content) {
　　print "The $element_name is $content/n<br>";
}

echo "<hr>";
print_r($xml);
echo $xml->channel->item[0]->asXML();
?>

任何XML文本在输出前最好用 htmlentiteis() 函数编码后再输出,否这可能出现问题