简单实用的cache类

[code]<?php

class Cache extends Base {

public $cacheDir = '/cache';
public $lifeTime = 3600;
public $dirLevels = 0; //缓存保存时的目录层数

private $md5id; //md5后的缓存id

const MAX_CACHE_DIR_LEVELS = 16; //最大缓存目录层次

public function __construct($config=array())
{
foreach ($config as $key=>$val) {
$this->$key=$val;
}

if ($this->dirLevels>self::MAX_CACHE_DIR_LEVELS) {
$this->dirLevels=self::MAX_CACHE_DIR_LEVELS;
}
}

/**
* 读取缓存
*
* @param string $id
* @return mixed|boolean
*/
public function get($id)
{
$this->md5id=md5($id);
$file=$this->getCacheFile($this->md5id);
if (is_file($file) && filemtime($file)>time()) {
return unserialize(file_get_contents($file));
} else {
return false;
}
}

/**
* 保存缓存
*
* @param mixed $data
* @param string $id
*/
public function save($data,$lifeTime=null,$id=null)
{
$lifeTime=time() + (strlen($lifeTime) ? $lifeTime : $this->lifeTime);
$md5id=strlen($id) ? md5($id) : $this->md5id;
$dir=$this->cacheDir.$this->getDirLevel($md5id);
if (!file_exists($dir)) {
mkdir($dir,0777,true);
}
$cacheFile=$dir.'/cache_'.$md5id;
file_put_contents($cacheFile,serialize($data),LOCK_EX);
touch($cacheFile,$lifeTime);
}

/**
* 获取缓存文件名
*
*/
private function getCacheFile($md5id)
{
return $this->cacheDir.$this->getDirLevel($md5id).'/cache_'.$md5id;
}

/**
* 获取缓存目录层次
*
*/
private function getDirLevel($md5id)
{
$levels=array();
$levelLen=2;
for ($i=0; $i<$this->dirLevels; $i++) {
$levels[]='cache_'.substr($md5id,$i*$levelLen,$levelLen);
}
return !count($levels) ? '' : '/'.implode('/',$levels);
}
}//class[/code]