/fuel/application/libraries/Cache.php

<?php  if (!defined('BASEPATH')) exit('No direct script access allowed');

//http://codeigniter.com/forums/viewthread/57117/
class Cache
{
	
	public $options = array(
						'cache_postfix' => '.cache',	//Prefix to all cache filenames
						'expiry_postfix' => '.exp',		//Expiry file prefix
						'group_postfix' => '.group', 	//Group directory prefix
						'default_ttl' => 3600  			//Default time to live = 3600 seconds (One hour).
					);
	
	/**
	 * 	Constructor
	 * 
	 * 	@param	Options to override defaults
	 */
	function __construct($options = NULL)
	{
		
		if ($options != NULL) $this->options = array_merge($this->options, $options);
		
	}
	
	/**
	 * 	Check if a item has a (valid) cache
	 * 
	 * 	@param	Cache id
	 * 	@param	Cache group id (optional)
	 * 	@return Boolean indicating if cache available
	 */
	function is_cached($cache_id, $cache_group = NULL)
	{
		
		if ($this->_get_expiry($cache_id, $cache_group) > time()) return TRUE;
		
		$this->remove($cache_id, $cache_group);
		
		return FALSE;
		
	}
	
	/**
	 * 	Save an item to the cache
	 * 
	 * 	@param	Cache id
	 * 	@param	Data object
	 * 	@param	Cache group id (optional)
	 * 	@param	Time to live for this item
	 */
	function save($cache_id, $data, $cache_group = NULL, $ttl = NULL)
	{
		
		if ($cache_group !== NULL)
		{
		
			$group_dir = $this->_group_dir($cache_group);
			
			if (!file_exists($group_dir)) mkdir($group_dir);
			
		}

		$file = $this->_file($cache_id, $cache_group);
		$cache_file = $file.$this->options['cache_postfix'];
		$expiry_file = $file.$this->options['expiry_postfix'];
		
		if ($ttl === NULL) $ttl = $this->options['default_ttl'];

		//
		//	Ok, so setting ttl = 0 is not quite forever, but 1000 years
		//	Is your PHP code going to be running for 1000 years? If so dont use this library (or just regenerate the cache then)!
		//
		if ($ttl == 0) $ttl = 31536000000; //1000 years in seconds
				
		$expire_time = time() + $ttl;		
				
	    $f1 = fopen($expiry_file, 'w');
		$f2 = fopen($cache_file, 'w');
		
	    flock($f1, LOCK_EX);
		flock($f2, LOCK_EX);
		
		fwrite($f1, $expire_time);
		fwrite($f2, serialize($data));
		
		flock($f1, LOCK_UN);
		flock($f2, LOCK_UN);
		
		fclose($f1);
		fclose($f2);
		
	}
	
	/**
	 * 	Get and return an item from the cache
	 * 
	 * 	@param	Cache Id
	 * 	@param	Cache group Id
	 * 	@param	Should I check the expiry time?
	 * 	@return The object or NULL if not available
	 */
	function get($cache_id, $cache_group = NULL, $skip_checking = FALSE)
	{
		
		if (!$skip_checking && !$this->is_cached($cache_id, $cache_group)) return NULL;

		$cache_file = $this->_file($cache_id, $cache_group).$this->options['cache_postfix'];
		
		if (!is_file($cache_file)) return NULL;

		return unserialize(file_get_contents($cache_file));
		
	}
	
	/**
	 * 	Remove an item from the cache
	 * 
	 * 	@param	Cache Id
	 * 	@param 	Cache group Id
	 */
	function remove($cache_id, $cache_group = NULL)
	{
		
		$file = $this->_file($cache_id, $cache_group);
		$cache_file = $file.$this->options['cache_postfix'];
		$expiry_file = $file.$this->options['expiry_postfix'];
		
		@unlink($cache_file);
		@unlink($expiry_file);
		
	}
	
	/**
	 * 	Remove an entire group
	 * 
	 * 	@param	Cache group Id
	 */
	function remove_group($cache_group)
	{
		
		$group_dir = $this->_group_dir($cache_group);
		
		//
		//	Empty the directory
		//
		if (!file_exists($group_dir) || !$dh = @opendir($group_dir)) return;
		
		while (($obj = readdir($dh))) {
		
		    if($obj=='.' || $obj=='..') continue;
	    	@unlink($group_dir.'/'.$obj);
		
		}
		
		closedir($dh);
		
		//
		//	Delete the dir for tidyness
		//
		@rmdir($group_dir);
		
	}
	
	/**
	 * 	Remove an array of cached items
	 * 
	 * 	@param	Array of cache ids
	 * 	@param	Cache group Id
	 */
	function remove_ids($cache_ids, $cache_group = NULL)
	{

		if (!is_array($cache_ids)) $cache_ids = array($cache_ids);

		//
		//	Hash all ids
		//
		$hashes = array();
		
		foreach($cache_ids as $cache_id)
		{
		
			$hashes[] = md5($cache_id);
			
		}

		$group_dir = $this->_group_dir($cache_group);
		
		//
		//	Delete matching files
		//
		if(!$dh = @opendir($group_dir)) return;
		
		$filecount = 0;
		$delcount = 0;
		
		while (($obj = readdir($dh))) {
		
		    if($obj=='.' || $obj=='..') continue;
		
			$parts = explode(".", $obj);
			$hash = $parts[0];
		
	    	if (in_array($hash, $hashes)) 
			{
				
				@unlink($group_dir.'/'.$obj);
				$delcount++;
				
			}
				
			$filecount ++;
		
		}
		
		closedir($dh);
		
		//
		//	Delete the dir if empty
		//
		if ($filecount == $delcount) @rmdir($group_dir);
		
	}
	
	//
	//	Private methods
	//
	
	private function _get_expiry($cache_id, $cache_group = NULL)
	{
		
		$file = $this->_file($cache_id, $cache_group).$this->options['expiry_postfix'];
	
		if (!is_file($file)) return 0;
		
		return intval(file_get_contents($file));
		
	}
	
	function _file($cache_id, $cache_group = NULL)
	{
		
		return $this->_group_dir($cache_group).'/'.md5($cache_id);
		
	}
	
	private function _group_dir($cache_group)
	{
		$CI =& get_instance();
		$dir = ($cache_group != NULL) ? md5($cache_group).$this->options['group_postfix'] : '';
		$cache_path = ($CI->config->item('cache_path') != '') ?  $CI->config->item('cache_path') : APPPATH.'cache/';
		return $cache_path.$dir;
		
	}
	
}
?>