Simple PHP caching

gistfile1.php

<?php

$key = md5('url-goes-here');
$cache_file = getcwd() . "/{$key}";

if (file_exists($cache_file))
{
  $html = file_get_contents($cache_file);
  echo 'reading from cache';
}
else
{
  $html = 'foo'; // remote request
  file_put_contents($cache_file, $html);
  echo 'reading from remote';
}

echo "\n{$html}";