<?php
// 
// Simple REQUEST_URI-based caching system
//   author: hide@address.com
// * require output buffering to be enabled
//
// example use:
// include("class.URI_Cache.php");
// $c = new URI_Cache(); // with just 1 line of code to enable auto caching.
// $c = new URI_Cache(10); // set duration to 10 seconds

class URI_Cache
{
	var $cache_dir = "/.cache_pages";
	var $cache_duration = 30;  // cache duration, in seconds
	var $cache_ext = ".html";
	var $debug = 0;
	var $need_cache = true;

	//class constructor, take care of cache directory creation
	//if autorun set to false, call Load() manually to load from cache
	function URI_Cache($dur=0,$dir='',$ext='',$load_and_exit=true)
	{
	    if (!ob_list_handlers())
		{
			if ($this->debug)
				print("Warning: Output buffering is not enabled. I am enabling it.");
			ob_start('ob_gzhandler');
		}
		
		if ($dur) $this->cache_duration = $dur;
		if ($dir) $this->cache_dir = $dir;
		if ($ext) $this->cache_ext = $ext;
		
	    $this->cache_dir = $_SERVER['DOCUMENT_ROOT']."/".$this->cache_dir;
		if ($load_and_exit) $this->Load();

	    // check if output buffering is enabled...
		if (!file_exists($this->cache_dir))
		{
	        mkdir($this->cache_dir);
	        chmod($this->cache_dir,0777);
		}
	}
	
	function __destruct()
	{
	    if ($this->need_cache) return $this->CachePage();
	}

	// load cached content.
	// if exit is true, output cached content and exit() when load success
	// if exit is false, return cached content
	function Load($exit=true)
	{
	    $cachefile = "$this->cache_dir/".md5($_SERVER['REQUEST_URI']).$this->cache_ext;
	    if (file_exists($cachefile))
		{
			if (filemtime($cachefile) > time()-$this->cache_duration)
			{
				$this->need_cache = false;
				if ($exit) {
					print file_get_contents($cachefile);
					if ($this->debug) print "<br />This page is cached by interval of $this->cache_duration.<br />Now: ".time();
					exit;
				}
				return file_get_contents($cachefile);
			}
			else
			    unlink($cachefile); // delete expired cache
		}
		return false;
	}

	//  cache the current page
	function CachePage()
	{
	    $cachefile = "$this->cache_dir/".md5($_SERVER['REQUEST_URI']).$this->cache_ext;
	    if ($this->debug) print "<br />Cached: ".time();
	    file_put_contents($cachefile, ob_get_contents());
	    if ($this->debug) print "<br />Cache renewed\n";
	}
}
?>