Search for all <wp:post_type> in a WXR file

parse.php

<?php
$input_file = '/path/to/wxr.wordpress.2013-07-16.xml';

$file = simplexml_load_file($input_file);
$output = fopen($input_file . '.txt', 'w');

// find all instances of <wp:post_type>
$matches = $file->xpath('//wp:post_type');
foreach($matches as $match) {
	// write out the contents
	fwrite($output, $match->__toString() . "\n");
}
fclose($output);