Detailed explanation of how PHP uses DOMDocument to operate xml

This article mainly introduces the method of PHP parsing and generating xml based on DOMDocument. It analyzes various common operating techniques of PHP using DOMDocument to parse xml nodes and generate xml files based on specific examples. Friends who need it can refer to it

The example in this article describes the method of PHP parsing and generating xml based on DOMDocument. Sharing it with you for your reference, the details are as follows:

I have shared with you some knowledge about SimpleXML operating xml, but in PHP there is also DOMDocument in addition to simplexml. This time I will focus on the usage of DOMDocument. Generate xml and parse xml separately

1. xml generation

DOMDocument operation xml is a little more complicated than the previous simplexml, I think simplexml is like dom4j in Java, the principle is the same no matter what. If the nodes and attributes in the DOMDocument are regarded as branches and leaves, then the DOMDocument of the DOMDocument is the root, and the nodes and attributes are all mounted under this object. It will be clear if you look at the following code

<?php
 $doc=new DOMDocument(&#39;1.0&#39;,&#39;utf-8&#39;);
 //创建根节点
 $root=$doc->createElement("StudentInfo");
 //创建第一个子节点
 $item=$doc->createElement("Item");
 $name=$doc->createElement("name","蔡依林");
 $studentnum=$doc->createElement("num","2009010502");
 //创建属性（phpdom可以把任何元素当做子节点）
 $id=$doc->createAttribute("id");
 $value=$doc->createTextNode(&#39;1&#39;);
 $id->appendChild($value);
 //在父节点下面加入子节点
 $item->appendChild($name);
 $item->appendChild($studentnum);
 $item->appendChild($id);
 $item2=$doc->createElement("Item");
 $name2=$doc->createElement("name","潘玮柏");
 $studentnum2=$doc->createElement("num","2009010505");
 $id2=$doc->createAttribute("id");
 $value2=$doc->createTextNode(&#39;2&#39;);
 $id2->appendChild($value2);
 $item2->appendChild($name2);
 $item2->appendChild($studentnum2);
 $item2->appendChild($id2);
 $root->appendChild($item);
 $root->appendChild($item2);
 //把根节点挂载在DOMDocument对象
 $doc->appendChild($root);
 header("Content-type: text/xml");
 //在页面上输出xml
 echo $doc->saveXML();
 //将xml保存成文件
 $doc->save("stu.xml");
?>

This code is actually not complicated if you look carefully. There may be some doubts about the id attribute, and the text node is also It must be mounted under DOMDocument, and then the text node is mounted under the attribute. Let’s take a look at the generated xml

In fact, DOMDocument generates nodes or attributes first, and the hierarchical relationship of xml is finally reflected through addchild

2. DOMDocument parsing

<?php
 $doc=new DOMDocument();
 //如果是解析xml字符串则使用loadXML
 $doc->load(&#39;stu.xml&#39;);
 //取得根节点
 $root=$doc->documentElement;
 //通过标记的名字取得对应的元素
 $items=$root->getElementsByTagName(&#39;Item&#39;);
 foreach($items as $key=>$val){
  // echo count($val->attributes);
  //id是第一个属性所以使用item(0),nodeValue用来取得节点的值
  echo $val->attributes->item(0)->name.":".$val->attributes->item(0)->nodeValue."  ";
  foreach($val->getElementsByTagName(&#39;name&#39;) as $key2=>$val2){
    echo $val2->nodeValue."  ";
  }
  foreach($val->getElementsByTagName(&#39;num&#39;) as $key3=>$val4){
    echo $val4->nodeValue."</br>";
  }
 }
?>

The focus of parsing is understanding. The getElementsByTagName method, attributes attributes and items are the focus of parsing xml. Everything else is pretty simple. Look at what is parsed

Generally speaking, it is a little more troublesome than simplexml, but as a programmer, it can be accepted.

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