dev-routing.php

<?php

declare(strict_types=1);

/**
 * I actually learned something about php's internal server with this file.
 * If you return false for a file that exists, php will default to
 * resolve it an return it.
 */
$root = $_SERVER['DOCUMENT_ROOT'];

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

if (file_exists($root.$path)) {
    // Enforces trailing slash, keeping links tidy in the admin
    if (is_dir($root.$path)
        && substr($path, -1) !== '/') {
        header("Location: $path/");

        exit;
    }

    // Runs PHP file if it exists
    if (strpos($path, '.php') !== false) {
        chdir(dirname($root.$path));

        if (false === include $root.$path) {
            /** @noinspection ForgottenDebugOutputInspection */
            error_log('Failed including file :: '.$root.$path.PHP_EOL);

            exit(1);
        }

        return true;
    }

    if (0 === strpos($path, '/wp-admin')) {
        return false;
    }
}

// Otherwise, run `index.php`
chdir($root);

require_once __DIR__.DIRECTORY_SEPARATOR.'index.php';