src/Storage/Memcached.php
public function has($uid) {
        if (null === $this->memcached) {
            return false;
        }
        $data = $this->read($uid);
        return false !== $data;
    }
public function has($uid) {
        if (null === $this->memcached) {
            return false;
        }
        $data = $this->read($uid);
        return false !== $data;
    }
Test if has datas with $uid key
@param mixed $uid
@return boolean