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php xml读写操作实现代码

May 25, 2016 pm 04:42 PM
php

文章从最基础的什么是xml到最终于用实例告诉你如何利用php来读,写,删除,编辑xml文档,是一篇不错的xml讲解文档,有需要的同学可以收藏本文章.

什么是XML?

XML(eXtensible Markup Language)是国际标准化组织的标准通用标记语言SGML的子集,由以下规范组成:

可扩展样式语言(eXtensible Sytle Language , XSL) 

XML链接语言(XML Linking Language,包括Xpath、Xlink和Xpointer) 

XML名称空间(XML Namespace) 

在PHP5之前的版本对XML的处理存在很多的问题,例如XML工具之间只具有简单的关联、每个工具不能一起协同工作等,PHP5中的新XML扩展具有下列特点:

能够像一个整体一样协调工作,是一个标准化的XML库:libxml2,完全遵循W3C规范,更有效地处理数据,是你工作中合适的XML工具 

HTML和XML区别与联系?

HTML和XML都是SGML的子集,所以他们有很大的相似性,下面是XML相对于HTML具有的独特性:

可扩展性,用以定义需要的新标记。这对于今天的web是很有意义的 

结构,用于表示任意复杂程度的数据。从某种意义上说是一个小型的关系数据库 

校验,用以检查数据的结构正确性。通过DTD约束可以达到这一目的。 

媒体无关性,以多种格式发布内容,网页、手机显示的wml、其他媒体终端的显示等,厂商和平台中立,数据的表示与内容分离(这是与html本质区别,但现在流行的DIV+CSS设计思路与这种近似).

XML的元素区分大小写,任何元素都需要有结束标记,XML只有一个根元素,属性必须加上引号.

一个完整的XML长什么样子,代码如下:

<?xml version="1.0">
<shows> 
    <show> 
        <name>Simpsons</name> 
        <channel>FOX</channel> 
        <start>8:00 PM</start> 
        <duration>30</duration> 
    </show> 
    <show> 
        <name>Law & Order</name> 
        <channel>NBC</channel> 
        <start>8:00 PM</start> 
        <duration>60</duration> 
    </show> 
</shows>
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形式良好的XML文档须具备下列特征:

每一个元素有一个开始和结束标记,文档有且只有一个根元素,其他的所有元素都是它的子元素,正确的格式化空元素,标记的大小写匹配,正确的嵌套,属性值必须用引号,实体在引用之前必须声明,实体不能循环指向自身.

通过DOM生成XML,代码如下:

// 创建一个新的文档$dom = new DOMDocument(&#39;1.0&#39;); 
// 创建一个根元素<book>并将其添加到文档$book = $dom->appendChild($dom->createElement(&#39;book&#39;)); 
// 创建一个title子元素,并添加到$book中 
$title = $book->appendChild($dom->createElement(&#39;title&#39;)); 
// 设置title元素的文本及cover属性 
$title->appendChild($dom->createTextNode(&#39;PHP Cookbook&#39;)); 
$title->setAttribute(&#39;cover&#39;, &#39;soft&#39;); 
// 创建并将author元素添加到$book中 
$sklar = $book->appendChild($dom->createElement(&#39;author&#39;)); 
//添加文本到author节点$sklar->appendChild($dom->createTextNode(&#39;Sklar&#39;)); 
$trachtenberg = $book->appendChild($dom->createElement(&#39;author&#39;)); 
$trachtenberg->appendChild($dom->createTextNode(&#39;Trachtenberg&#39;)); 
// 输出完美格式化的XML文档$dom->formatOutput = true; 
echo $dom->saveXML();//输出内容如下:
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<?xml version="1.0" 
<book 
  <cover="soft">PHP Cookbook</title> 
</book>
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用PHP解析已经存在的XML文件,常用有三种方式来解析XML文件,对于简单文件采用SimpleXML,对于复杂的XML文件采用DOM扩展来实现,对于大型XML文件采用XMLReader扩展来实现.

XML示例文件如下address-book.xml,代码如下:

<?xml version="1.0" 
<address-book> 
    <person id="1"> 
        <!--David Sklar--> 
        <firstname>David</firstname> 
        <lastname>Sklar</lastname> 
        <city>New York</city> 
        <state>NY</state> 
        <email>sklar@php.net</email> 
    </person> 
 
    <person id="2"> 
        <!--Adam Trachtenberg--> 
        <firstname>Adam</firstname> 
        <lastname>Trachtenberg</lastname> 
        <city>San Francisco</city> 
        <state>CA</state> 
        <email>amt@php.net</email> 
    </person> 
</address-book>
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通过SimpleXML方式,代码如下:

$sx = simplexml_load_file(&#39;address-book.xml&#39;); 
foreach ($sx->person as $person) { 
    $firstname_text_value = $person->firstname; 
    $lastname_text_value = $person->lastname; 
    print "$firstname_text_value $lastname_text_valuen"; 
}
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通过DOM扩展,代码如下:

$dom = new DOMDocument; 
$dom->load(&#39;address-book.xml&#39;); 
 
foreach ($dom->getElementsByTagname(&#39;person&#39;) as $person) { 
    $firstname = $person->getElementsByTagname(&#39;firstname&#39;); 
    $firstname_text_value = $firstname->item(0)->firstChild->nodeValue; 
 
    $lastname = $person->getElementsByTagname(&#39;lastname&#39;); 
    $lastname_text_value = $lastname->item(0)->firstChild->nodeValue; 
 
    print "$firstname_text_value $lastname_text_valuen"; 
}
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通过XMLReader扩展,代码如下:

$reader = new XMLReader(); 
$reader->open(&#39;card-catalog.xml&#39;); 
 
while ($reader->read()) { 
    if ($reader->nodeType == XMLREADER::ELEMENT && $reader->localName == &#39;author&#39;) { 
        $reader->read(); 
        print $reader->value . "n"; 
    } 
}
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在SimpleXML和DOM扩展中都有XPath,代码如下:

//SimpleXml示例 
$emails = $s->xpath(&#39;/address-book/preson/email&#39;); 
 
//DOM扩展示例 
$xpath = new DOMXPath($dom); 
$email = $xpath->query(&#39;/address-book/preson/email&#39;);//验证XML文档是否合法
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在PHP中,DOM扩展支持基于DTD,XML Schema和RelaxNG的验证,而SimpleXML则只提供了XML Schema验证.

XML内容为UTF-8格式

如果数据来源为其他格式,需要经过编码为UTF-8格式,下面是通过iconv库进行转换的示例,代码如下:

$utf_8 = iconv('ISO-8859-1', 'UTF-8', $iso_8859_1);


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