Pretty print XML in PHP

As part of my freelance work I send data to APIs, often using XML for data transfer. I log the XML sent and received for debugging and auditing, however the XML often has no line breaks or indentation, making it difficult to read.

Fortunately there’s a simple way to pretty print or format XML strings in PHP, by using the DOMDocument class with a few parameters. I’ve used a hardcoded XML string in the example below, but if you have a SimpleXmlElement object the asXML function will return the XML as a string.

<?php

$xml = '<test><a><b></b></a><c></c></test>';
$dom = new \DOMDocument('1.0');
$dom->preserveWhiteSpace = true;
$dom->formatOutput = true;
$dom->loadXML($xml);
$xml_pretty = $dom->saveXML();

The output of running the above code is:

<?xml version="1.0"?>
<test>
  <a>
    <b/>
  </a>
  <c/>
</test>