[PHP] ファイルの大文字小文字を吸収

.htaccess

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* /canonical.php [L]
</IfModule>

canonical.php

<?php
function not_found($message = '') {
  header("HTTP/1.1 404 Not Found");
  echo $message."\n";
  die();
}

if (!isset($_SERVER['REQUEST_URI']))
  not_found();

$uri = htmlspecialchars($_SERVER['REQUEST_URI']);
if ($uri === '/canonical.php')
  not_found();

$dir = dirname(__FILE__).dirname($uri).'/';
if (!file_exists($dir))
  not_found("{$uri} is not found.");

$file = pathinfo(basename($uri));
$name = isset($file['filename'])  ? $file['filename'] : '';
$ext  = isset($file['extension']) ? '.'.$file['extension'] : '';

$filenames = array(
  $name . strtolower($ext),
  strtolower($name) . $ext,
  strtolower($name) . strtolower($ext),
  strtolower($name) . strtoupper($ext),
  $name . strtoupper($ext),
  strtoupper($name) . $ext,
  strtoupper($name) . strtoupper($ext),
  strtoupper($name) . strtolower($ext),
);
foreach ($filenames as $filename) {
  if (file_exists($dir.$filename)) {
    header('HTTP/1.1 301 Moved Permanently');
    header('Location: '.dirname($uri).'/'.$filename);
    exit();
  }
}

not_found("{$uri} is not found.");