How to use XML in PHP

XML is a data format frequently used in web development. As a general scripting language, PHP can easily parse and generate XML documents. In this article, I will introduce how to use XML in PHP.

1. Parsing XML

PHP provides a built-in XML parser that can easily convert XML documents into corresponding PHP data structures. The following is a simple example that demonstrates how to parse an XML file:

<?php

$xmlString = <<<XML
<root>
  <item>
    <name>Apple</name>
    <price>1.99</price>
  </item>
  <item>
    <name>Banana</name>
    <price>0.99</price>
  </item>
</root>
XML;

$xml = simplexml_load_string($xmlString);

foreach ($xml->item as $item) {
    echo $item->name . ": " . $item->price . "
";
}

?>

For the above code, we first define an XML string and convert it into a PHP object using the simplexml_load_string() method. Subsequently, we used a foreach loop to iterate over each product node and output their name and price. The output of this code snippet should be:

Apple: 1.99
Banana: 0.99

2. Generate XML

PHP also provides many methods and functions to help us generate XML documents. The following is a simple example that demonstrates how to use PHP to generate an XML document:

<?php

// 创建XML对象
$xml = new SimpleXMLElement('<root></root>');

// 添加商品
$item1 = $xml->addChild('item');
$item1->addChild('name', 'Apple');
$item1->addChild('price', '1.99');

$item2 = $xml->addChild('item');
$item2->addChild('name', 'Banana');
$item2->addChild('price', '0.99');

// 输出XML
echo $xml->asXML();

?>

In the above code, we first create an XML node named root. Subsequently, we add child nodes, namely two items, to the node through the addChild() function. Finally, we output the generated XML document to the standard output stream. The output of this code snippet should be:

<?xml version="1.0"?>
<root>
  <item>
    <name>Apple</name>
    <price>1.99</price>
  </item>
  <item>
    <name>Banana</name>
    <price>0.99</price>
  </item>
</root>

3. Using the DOM API

In addition to the simplexml_load_string() and SimpleXMLElement classes, PHP also provides a DOM API for parsing and generate XML documents. The DOM API provides many powerful methods and functions that can help us process XML documents more flexibly. The following are some simple examples of using the DOM API:

<?php

// 解析XML
$dom = new DOMDocument();
$dom->load('data.xml');
$xpath = new DOMXPath($dom);
$items = $xpath->query('/root/item');

foreach ($items as $item) {
    $name = $xpath->query('name', $item)->item(0)->nodeValue;
    $price = $xpath->query('price', $item)->item(0)->nodeValue;
    echo $name . ": " . $price . "
";
}

// 生成XML
$dom = new DOMDocument();
$root = $dom->createElement('root');
$dom->appendChild($root);

$item1 = $dom->createElement('item');
$item1->appendChild($dom->createElement('name', 'Apple'));
$item1->appendChild($dom->createElement('price', '1.99'));
$root->appendChild($item1);

$item2 = $dom->createElement('item');
$item2->appendChild($dom->createElement('name', 'Banana'));
$item2->appendChild($dom->createElement('price', '0.99'));
$root->appendChild($item2);

echo $dom->saveXML();

?>

In the above code, we first use the DOMDocument class and DOMXPath class to parse an XML document named data.xml, and use XPath syntax to query all products node. We then process the name and price of each item and output them to the standard output stream.

Next, we generated an XML document using the DOM API. We first created an XML node named root and added two child nodes to it, namely two items. The code snippet finally outputs the generated XML document.

4. Summary

In this article, we learned how to use XML in PHP. We introduced how to parse XML documents, generate XML documents, and how to use the DOM API to process XML documents. I hope this article is helpful to you. If you want to learn more about PHP about XML, you can refer to the XML chapter in the PHP official documentation.

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