php cache

<?php

$url = 'http://www.site.com/file.php';
$dest_file = 'footercache.txt'; //be sure it is chmod-ed to 0666  !!
//Note: for requests by keyword use a cache folder whose rights are 0777 and define the destination file as 
//$dest_file = CACHE_FOLDER . '/cache-' . preg_replace('/[^a-z0-9]+/','_', $keyword) . '.txt';
//this may need changes on the line checking the length of the dest_file


$pagesource = request_cache($url, $dest_file, 3600*24*7);
echo $pagesource;

function request_cache($url, $dest_file, $timeout=7200) {
 if(strlen($dest_file) > 100) $dest_file = substr($dest_file, 20, 60) . substr($dest_file, strlen($dest_file) - 4);//keep some chars and the probable extension

 if(!file_exists($dest_file) || filemtime($dest_file) < (time()-$timeout)) {
  $data = @file_get_contents($url);
  if ($data !== false) {
   $tmpf = tempnam('/tmp','YWS');
   $fp = @fopen($tmpf,"w");
   @fwrite($fp, $data);
   @fclose($fp);
   if(file_exists($dest_file)) @unlink($dest_file);
   rename($tmpf, $dest_file);
  }else{
    touch($dest_file);//update its date only
  }
 } else {
  $data = file_get_contents($dest_file);
 }
 return($data);
}

?>