PHP XML Parser

XML Parsing Methods

🔹 SimpleXML - Load from String

Parse XML data from a string using simplexml_load_string(). This is the easiest way to work with XML when you have the XML content as a string variable.

<?php
$xmlString = '<?xml version="1.0"?>
<book>
    <title>PHP Basics</title>
    <author>John Doe</author>
    <price>29.99</price>
</book>';

$xml = simplexml_load_string($xmlString);
echo "Title: " . $xml->title;
echo "<br>Author: " . $xml->author;
echo "<br>Price: $" . $xml->price;
?>

🔹 SimpleXML - Load from File

Read XML data directly from a file using simplexml_load_file(). This method is perfect for processing XML configuration files or data feeds stored on disk.

<?php
// Assuming books.xml exists with book data
$xml = simplexml_load_file('books.xml');

foreach ($xml->book as $book) {
    echo "Title: " . $book->title . "<br>";
    echo "Author: " . $book->author . "<br><br>";
}

// Alternative: check if file loaded
if ($xml === false) {
    echo "Failed to load XML file";
}
?>

🔹 Accessing XML Attributes

Extract attribute values from XML elements using array syntax. Attributes provide additional information about elements and are commonly used in XML documents.

<?php
$xmlString = '<?xml version="1.0"?>
<catalog>
    <product id="101" category="electronics">
        <name>Laptop</name>
        <price currency="USD">999</price>
    </product>
</catalog>';

$xml = simplexml_load_string($xmlString);
$product = $xml->product;

echo "Product ID: " . $product['id'];
echo "<br>Category: " . $product['category'];
echo "<br>Name: " . $product->name;
echo "<br>Price: " . $product->price . " " . $product->price['currency'];
?>

🔹 DOM Parser - Basic Usage

Use DOMDocument for more complex XML operations. DOM provides full control over XML structure, allowing you to modify, add, or remove elements and attributes.

<?php
$xmlString = '<?xml version="1.0"?>
<users>
    <user>
        <name>Alice</name>
        <email>[email protected]</email>
    </user>
    <user>
        <name>Bob</name>
        <email>[email protected]</email>
    </user>
</users>';

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

$users = $dom->getElementsByTagName('user');
foreach ($users as $user) {
    $name = $user->getElementsByTagName('name')[0]->nodeValue;
    $email = $user->getElementsByTagName('email')[0]->nodeValue;
    echo "Name: $name, Email: $email<br>";
}
?>

🔹 Creating XML with SimpleXML

Build XML documents programmatically using SimpleXML. You can create new elements, add attributes, and generate complete XML structures from PHP data.

<?php
// Create new XML document
$xml = new SimpleXMLElement('<catalog/>');

// Add book element
$book = $xml->addChild('book');
$book->addChild('title', 'Learning PHP');
$book->addChild('author', 'John Smith');
$book->addChild('year', '2024');
$book->addAttribute('isbn', '978-1234567890');

// Output formatted XML
echo htmlspecialchars($xml->asXML());
?>

🔹 XPath Queries

Search XML documents using XPath expressions. XPath provides a powerful way to locate specific elements based on their path, attributes, or content within the XML structure.

<?php
$xmlString = '<?xml version="1.0"?>
<library>
    <book category="fiction">
        <title>The Great Novel</title>
        <price>15.99</price>
    </book>
    <book category="science">
        <title>Physics 101</title>
        <price>45.00</price>
    </book>
</library>';

$xml = simplexml_load_string($xmlString);

// Find all fiction books
$fiction = $xml->xpath('//book[@category="fiction"]');
foreach ($fiction as $book) {
    echo "Fiction: " . $book->title . "<br>";
}

// Find books under $20
$cheap = $xml->xpath('//book[price < 20]');
echo "Affordable: " . $cheap[0]->title;
?>

🔹 Error Handling

Handle XML parsing errors gracefully to prevent application crashes. Always validate XML input and check for parsing errors before processing the data.

<?php
$xmlString = '<invalid><xml>'; // Malformed XML

libxml_use_internal_errors(true);
$xml = simplexml_load_string($xmlString);

if ($xml === false) {
    echo "Failed to parse XML:<br>";
    foreach (libxml_get_errors() as $error) {
        echo "- " . $error->message . "<br>";
    }
    libxml_clear_errors();
} else {
    echo "XML parsed successfully";
}
?>