Simple PHP caching function

cacher.php

<?php
  $handle = opendir('_cache/');
	while (false !== ($entry = readdir($handle))) {
        if (strlen($entry) > 2){
        	$a = explode(".", $entry);
        	$a = explode("_", $a[0]);
        	$tstamp = intval($a[1]);
        	$t = time();
        	if ($t > ($tstamp + 12)){
        		// do the call, rewrite the timestamp
        		rename("_cache/" . $entry, "_cache/file_" . $t . ".cache");
        		echo file_get_contents("_cache/file_" . $t . ".cache");
        	} else {
        		echo file_get_contents("_cache/" . $entry);
        	}
        }
    }
?>

This relies on a pre-existing _cache folder and file_xxxx.cache file. The check for the strlen of $entry is to prevent . or .. from being considered cache files. Only intended for one cache file, one call, etc.