PHP XML Parsers

Types of XML Parsers

🔹 SimpleXML Parser

SimpleXML converts XML into an object that can be processed with normal property selectors. It's the easiest parser for beginners:

<?php
// XML data
$xmlString = '<?xml version="1.0"?>
<library>
    <book>
        <title>PHP Programming</title>
        <author>John Smith</author>
        <price>29.99</price>
    </book>
</library>';

// Parse XML
$xml = simplexml_load_string($xmlString);

// Access data
echo "Title: " . $xml->book->title . "<br>";
echo "Author: " . $xml->book->author . "<br>";
echo "Price: $" . $xml->book->price;
?>

🔹 DOM Parser

The DOM parser loads the entire XML document into memory as a tree structure, allowing full manipulation of the document:

<?php
$xmlString = '<?xml version="1.0"?>
<students>
    <student id="1">
        <name>Alice</name>
        <grade>A</grade>
    </student>
    <student id="2">
        <name>Bob</name>
        <grade>B</grade>
    </student>
</students>';

// Create DOM document
$dom = new DOMDocument();
$dom->loadXML($xmlString);

// Get all student elements
$students = $dom->getElementsByTagName('student');

foreach ($students as $student) {
    $id = $student->getAttribute('id');
    $name = $student->getElementsByTagName('name')->item(0)->nodeValue;
    $grade = $student->getElementsByTagName('grade')->item(0)->nodeValue;
    
    echo "Student $id: $name - Grade: $grade<br>";
}
?>

🔹 XMLReader Parser

XMLReader is a pull parser that reads XML node by node, making it memory-efficient for large files:

<?php
// Create XML file content
$xmlContent = '<?xml version="1.0"?>
<products>
    <product>
        <name>Laptop</name>
        <price>999</price>
    </product>
    <product>
        <name>Mouse</name>
        <price>25</price>
    </product>
</products>';

// Save to temporary file
$tempFile = 'temp.xml';
file_put_contents($tempFile, $xmlContent);

// Create XMLReader
$reader = new XMLReader();
$reader->open($tempFile);

// Read through XML
while ($reader->read()) {
    if ($reader->nodeType == XMLReader::ELEMENT && $reader->name == 'product') {
        $reader->read(); // Move to name
        $name = $reader->readString();
        $reader->next(); // Skip to price
        $reader->read();
        $price = $reader->readString();
        
        echo "Product: $name - Price: $$price<br>";
    }
}

$reader->close();
unlink($tempFile); // Clean up
?>

🔹 Expat Parser (Event-Based)

Expat is an event-based parser that triggers callback functions when it encounters XML elements:

<?php
// XML data
$xmlData = '<?xml version="1.0"?>
<note>
    <to>John</to>
    <from>Jane</from>
    <message>Hello!</message>
</note>';

// Create parser
$parser = xml_parser_create();

// Element handlers
function startElement($parser, $name, $attrs) {
    echo "<b>Start: $name</b><br>";
}

function endElement($parser, $name) {
    echo "<i>End: $name</i><br>";
}

function characterData($parser, $data) {
    $data = trim($data);
    if (!empty($data)) {
        echo "Data: $data<br>";
    }
}

// Set handlers
xml_set_element_handler($parser, "startElement", "endElement");
xml_set_character_data_handler($parser, "characterData");

// Parse XML
xml_parse($parser, $xmlData);

// Free parser
xml_parser_free($parser);
?>

🔹 Choosing the Right Parser

Select a parser based on your specific needs and XML document characteristics:

🔹 Parser Performance Tips