PHP XML Expat Parser

⚡ PHP XML Expat Parser Tutorial

PHP provides an Expat-based XML parser (xml_parser_create) for event-driven XML parsing. It is also called a SAX parser because it reads XML sequentially, triggering events for start elements, end elements, and character data.

This method is useful for large XML files where loading the entire file into memory is inefficient.

1️⃣ Basic Example

<?php
// Event handler functions
function startElement($parser, $name, $attrs) {
echo "Start Element: $name<br>";
if (!empty($attrs)) {
foreach ($attrs as $attr => $value) {
echo " - Attribute: $attr = $value<br>";
}
}
}

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

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

// Create parser
$xml_parser = xml_parser_create();

// Assign event handlers
xml_set_element_handler($xml_parser, "startElement", "endElement");
xml_set_character_data_handler($xml_parser, "characterData");

// Load XML data
$xml_data = file_get_contents("users.xml");

// Parse XML
if (!xml_parse($xml_parser, $xml_data, true)) {
die(sprintf("XML Error: %s at line %d",
xml_error_string(xml_get_error_code($xml_parser)),
xml_get_current_line_number($xml_parser)));
}

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

<?php

// Event handler functions

function startElement($parser, $name, $attrs) {

echo "Start Element: $name<br>";

if (!empty($attrs)) {

foreach ($attrs as $attr => $value) {

echo " - Attribute: $attr = $value<br>";

}

function endElement($parser, $name) {

echo "End Element: $name<br>";

}

function characterData($parser, $data) {

$data = trim($data);

if (!empty($data)) {

echo "Data: $data<br>";

}

// Create parser

$xml_parser = xml_parser_create();

// Assign event handlers

xml_set_element_handler($xml_parser, "startElement", "endElement");

xml_set_character_data_handler($xml_parser, "characterData");

// Load XML data

$xml_data = file_get_contents("users.xml");

// Parse XML

if (!xml_parse($xml_parser, $xml_data, true)) {

die(sprintf("XML Error: %s at line %d",

xml_error_string(xml_get_error_code($xml_parser)),

xml_get_current_line_number($xml_parser)));

}

// Free parser

xml_parser_free($xml_parser);

2️⃣ Sample XML (`users.xml`)

Output:

3️⃣ Key Points

Event-driven parser – triggers functions on start element, end element, and character data.
Efficient for large XML files; does not load entire XML into memory.
Event handler functions receive:
- $parser – the parser resource
- $name – element name
- $attrs – array of attributes
- $data – text data inside elements
Always free parser with xml_parser_free().
Error handling is possible with xml_get_error_code() and xml_get_current_line_number().

PHP XML Expat Parser