PHP Caching Snippet adapted from Peter Karman

php_caching_snippet.php

<?php

// Sample Usage
$uri_to_fetch = 'http://example.tld/path/to/uri';

$cache_on  = true;
$cache_key = md5( $uri_to_fetch );
$cache_ttl = 60 * 15;   // 15 minutes
$cache_file = '/tmp/example.tld/'.$cache_key;
if (file_exists($cache_file) &&
   (time() - $cache_ttl) < filemtime($cache_file) &&
   $cache_on
) {
   // use the cache
   $content = file_get_contents($cache_file);
}
else {
   // fetch the page and cache it
   $content = cache_file_get_contents($uri_to_fetch, $cache_file);
}

// Cache-Wrapper for file_get_contents

function cache_file_get_contents($uri, $cache_file) {

   if (!file_exists(dirname($cache_file))) {
     mkdir(dirname($cache_file));
   }
   
   $old_umask = umask(0007); // group-write-able, no world access
   if (!$fp=fopen($cache_file, 'w')) {
       throw new Exception('Error opening cache file');
       exit();
   }
   if (!flock($fp, LOCK_EX)) {
       throw new Exception('Unable to lock file');
       exit();
   }
   $buffer = file_get_contents($uri);

   // sanity check
   if (!strlen($buffer)) {
       // throw exception? read existing cache file?
   }
   if (!fwrite($fp, $buffer)) {
       throw new Exception('Error writing to cache file');
       exit();
   }
   flock($fp, LOCK_UN);
   fclose($fp);
   umask($old_umask); // restore

   return $buffer;
}