PHP XML DOM

Manipulate XML documents using the Document Object Model

🌳 What is XML DOM?

XML DOM (Document Object Model) treats XML documents as a tree structure. You can navigate, search, modify, and create XML elements easily using PHP's DOMDocument class. 


<?php
// Create new DOM document
$dom = new DOMDocument();
$dom->loadXML("<root><item>Hello DOM!</item></root>");

echo $dom->saveXML();
?>

Output:

<?xml version="1.0"?>
<root><item>Hello DOM!</item></root>

Key DOM Concepts

The DOM represents XML as a hierarchical tree where each element, attribute, and text is a node. You can traverse this tree, modify nodes, add new ones, or remove existing elements programmatically.

📂

Load XML

Load XML from string or file 

$dom = new DOMDocument();
$dom->load("file.xml");
🔍

Query Elements

Find elements by tag name 

$items = $dom
    ->getElementsByTagName("item");
➕

Create Elements

Add new XML elements 

$element = $dom
    ->createElement("item", "text");
💾

Save XML

Output XML to string or file 

$dom->save("output.xml");
echo $dom->saveXML();

🔹 Loading XML Documents

Load XML from different sources: 

<?php
// Method 1: Load from string
$dom = new DOMDocument();
$xmlString = "<books><book>PHP Guide</book></books>";
$dom->loadXML($xmlString);
echo "Loaded from string<br>";

// Method 2: Load from file
$dom2 = new DOMDocument();
$dom2->load("books.xml");
echo "Loaded from file<br>";

// Method 3: Create new document
$dom3 = new DOMDocument("1.0", "UTF-8");
$root = $dom3->createElement("catalog");
$dom3->appendChild($root);
echo "Created new document";
?>

Output:

Loaded from string
Loaded from file
Created new document

🔹 Reading XML Elements

Access and display XML element values: 

<?php
$xml = "<library>
    <book>PHP Basics</book>
    <book>Advanced PHP</book>
    <book>PHP Security</book>
</library>";

$dom = new DOMDocument();
$dom->loadXML($xml);

// Get all book elements
$books = $dom->getElementsByTagName("book");

echo "Total books: " . $books->length . "<br><br>";

// Loop through books
foreach ($books as $book) {
    echo "📚 " . $book->nodeValue . "<br>";
}
?>

Output:

Total books: 3

📚 PHP Basics
📚 Advanced PHP
📚 PHP Security

🔹 Working with Attributes

Read and set XML element attributes: 

<?php
$xml = '<books>
    <book id="101" lang="en">PHP Guide</book>
    <book id="102" lang="es">Guía PHP</book>
</books>';

$dom = new DOMDocument();
$dom->loadXML($xml);

$books = $dom->getElementsByTagName("book");

foreach ($books as $book) {
    $id = $book->getAttribute("id");
    $lang = $book->getAttribute("lang");
    $title = $book->nodeValue;
    
    echo "Book #$id ($lang): $title<br>";
}
?>

Output:

Book #101 (en): PHP Guide
Book #102 (es): Guía PHP

🔹 Creating XML Documents

Build XML documents from scratch: 

<?php
// Create document
$dom = new DOMDocument("1.0", "UTF-8");
$dom->formatOutput = true;

// Create root element
$root = $dom->createElement("students");
$dom->appendChild($root);

// Create student element
$student = $dom->createElement("student");
$root->appendChild($student);

// Add name element
$name = $dom->createElement("name", "John Doe");
$student->appendChild($name);

// Add age element
$age = $dom->createElement("age", "20");
$student->appendChild($age);

// Add attribute
$student->setAttribute("id", "S001");

// Output XML
echo htmlspecialchars($dom->saveXML());
?>

Output: 

<?xml version="1.0" encoding="UTF-8"?>
<students>
  <student id="S001">
    <name>John Doe</name>
    <age>20</age>
  </student>
</students>

🔹 Modifying XML

Update existing XML elements and attributes: 

<?php
$xml = '<product id="100">
    <name>Laptop</name>
    <price>500</price>
</product>';

$dom = new DOMDocument();
$dom->loadXML($xml);

// Change price
$price = $dom->getElementsByTagName("price")->item(0);
$price->nodeValue = "450";

// Update attribute
$product = $dom->getElementsByTagName("product")->item(0);
$product->setAttribute("id", "101");

// Add new element
$stock = $dom->createElement("stock", "In Stock");
$product->appendChild($stock);

echo htmlspecialchars($dom->saveXML());
?>

Output: 

<product id="101">
  <name>Laptop</name>
  <price>450</price>
  <stock>In Stock</stock>
</product>

🧠 Test Your Knowledge

What does DOM stand for?