Routing file for PHP's built-in web server to work on WordPress (and serve PDFs).

router.php

<?php
 
$root = $_SERVER['DOCUMENT_ROOT'];

chdir($root);

$path = '/'.ltrim(parse_url($_SERVER['REQUEST_URI'])['path'],'/');

if(file_exists($root.$path)) {
    if(is_dir($root.$path) && substr($path,strlen($path) - 1, 1) !== '/') {
        header('location: '.rtrim($path,'/').'/');
        exit;
    }
    
    if(preg_match('/\.(?:pdf)$/', $root.$path)) {
        header("Content-Type: application/pdf");
        readfile($root.$path);
    }
    else {
        return false;
    }
    
    if(strpos($path,'.php') === false) return false;
    else {
        chdir(dirname($root.$path));
        require_once $root.$path;
    }   
} else include_once 'index.php';

?>