使用ThinkPhp3.2.3 的S函数，键不能是小驼峰形式，会返回false

public function getAccessToken()
{
    $res = S("yZAccessToken");
    if ($res) {//这边都是false
        echo 1;//一直都是不会打印
        return $res;
    } else {
        $yZGetTokenClient = new YZGetTokenClient( $this->client_id , $this->client_secret );
        $accessToken =  $yZGetTokenClient->get_token($this->type, $this->keys);
        S("yzAccessToken", $accessToken["access_token"], $accessToken["expires_in"]);
        return $accessToken["access_token"];
    }

}

public function getAccessToken()
{
    $res = S("yzaccesstoken");
    if ($res) {

	echo 1;//这边缓存就有效果
        return $res;
    } else {
        $yZGetTokenClient = new YZGetTokenClient( $this->client_id , $this->client_secret );
        $accessToken =  $yZGetTokenClient->get_token($this->type, $this->keys);
        S("yzaccesstoken", $accessToken["access_token"], $accessToken["expires_in"]);
        return $accessToken["access_token"];
    }

}

具体未去看底层实现，有时间再研究