PHP script to strip entities from XML

gistfile1.txt

<?php
$unconvertedEntity = array(
  '&percnt;',
	'&numsp;',
	'&lowbar;'
);
$convertedChar = array(
	'%',
	' ',
	'_'
);

$filename = $argv[1];
$xml = file_get_contents($filename);
$xml = html_entity_decode($xml);
$xml = htmlspecialchars_decode($xml, ENT_HTML5);
$xml = str_replace($unconvertedEntity, $convertedChar, $xml);
$xml = str_replace('&', '&amp;', $xml);

file_put_contents('stripped/'.$filename, $xml);