beautifyXml.php

<?php

/**
 * @param string $sMarkup
 * @return string
 */
function beautifyXml($sMarkup = '') : string
{
    $oDOMDocument = new DOMDocument();
    $oDOMDocument->preserveWhiteSpace = false;
    $oDOMDocument->loadXML($sMarkup);
    $oDOMDocument->formatOutput = true;
    $sMarkup = $oDOMDocument->saveXml();
  
    return $sMarkup;
}