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”); // 本地文件系统,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