code: public function set(string $sName, $mValue, int $iFlag, int $iExpire)
      {
          file_put_contents($this->_sFolder.$this->_getSubDirectory($sName).md5($sName).'.fil.cac', serialize($mValue));
          return $this;
      }
docs: set a value
  
  @access public
  @param  string $sName name of the session
  @param  mixed $mValue value of this sesion var
  @param  int $iFlag flags
  @param  int $iExpire expiration of cache
  @return \Venus\lib\Cache\File