laravel4 缓存null值时cache失效

Question

public static function getUserById($id)
{
    $key = sprintf("%s_%s",__METHOD__, $id);

    $mdkey = md5($key);

    var_dump(Cache::tags(self::CACHE_TAG)->has($mdkey));die();

    if(Cache::tags(self::CACHE_TAG)->has($mdkey))
    {
        echo 'has cache';
        return Cache::tags(self::CACHE_TAG)->get($mdkey);
    }

    $user = User::where('uid',$id)->first();

    Cache::tags(self::CACHE_TAG)->put($mdkey, $user, self::CACHE_TIME);

    return $wifi;
}

---

在Repository中的has方法定义
/**
 * Determine if an item exists in the cache.
 *
 * @param  string  $key
 * @return bool
 */
public function has($key)
{
    return ! is_null($this->get($key));
}

如果缓存保存的值时null时，has都会返回false，如何区分用户保存的null和cache无保存时的null呢？

Answer 1

用"\0"之类的占位符代替null