public function getWxPayJsApiParameters($prepayId)
{
// 获取jsapi支付的参数
$input = ['appId' => $this->appId, 'timeStamp' => (string) time(), 'nonceStr' => SHA1::get_random_str(32), 'package' => 'prepay_id=' . $prepayId, 'signType' => 'MD5'];
// 签名
$input['paySign'] = SHA1::getSign2($input, 'key=' . $this->key);
return json_encode($input);
}