PHP文件缓存类

 <?php
     /**
      * @desc 文件缓存
      */
     class Cache{
         const C_FILE = '/Runtime/';
         private $dir = '';
         const EXT = '.tpl';
         private $filename = '';
         public function __construct($dir = ''){
             $this->dir = $dir;

         }
         /**
          *    @desc 设置文件缓存
          *    @param string $key 文件名
          *    @param unkonw $data 缓存数据
          *    @param int    $expire 过期时间
          */
         public function set($key,$data,$expire = 0){
             $this->filename =     dirname(__FILE__).self::C_FILE.$this->dir.$key.self::EXT;
             if(file_exists($this->filename)){
                 $res = $this->get($key);
                 if(md5($res) == md5(json_encode($data) ) ){
                     return true;
                 }
             }
             if(!is_dir(dirname($this->filename))){
                 mkdir(dirname($this->filename),0777);
             }

             $source = fopen($this->filename,'w+');
             fwrite($source,json_encode($data));
             fclose($source);
         }

         /**
          *    @desc 获取文件
          *  @param string $key 文件名
          */
         public function get($key){
             //$filename = dirname(__FILE__).self::C_FILE.$this->dir.$key.self::EXT;
             if(!file_exists($this->filename)){
                 return '缓存文件已经不存在';
             }else{
                 $res = file_get_contents($this->filename);
             }
             return $res;
         }
         /**
          *    @desc 删除文件
          *  @param string $key 文件名
          */
         public function del($key){
             unlink($this->filename);
         }

     }

     $data = array('name'=>'song','age'=>20,'sex'=>'man','favority'=>array('apple','banana'));
     $cache = new Cache();
     $cache->set('cache',$data);
     //$cache->get('cache');
     //$cache->del('cache');