在paytm的帮助下发送短信发票给出错误

Question

我想在paytm的帮助下发送短信发票

我的codeigniter

下面有代码

在third_party文件夹中我有paytm库，我已经调用过如下的api，

 $this->load->library('paytm');
        $paytm = $this->paytm->load();
        $paytm->PAYTM_POST_DATA["mid"] = "mystaggingmid";
        $paytm->PAYTM_POST_DATA["recipientName"] = 'hetal';
        $paytm->PAYTM_POST_DATA["recipientNumber"] = 'mycontactno';
        $paytm->PAYTM_POST_DATA["phoneType"] = "smart";
        $paytm->PAYTM_POST_DATA["invoiceId"] = '1234';
        $paytm->PAYTM_POST_DATA["expiryDate"] = '20/3/2018';
        $paytm->PAYTM_POST_DATA["taxType"] = "inclusive";
        $paytm->PAYTM_POST_DATA["discountType"] = 'beforetax';
        $paytm->PAYTM_POST_DATA["discountMode"] = 'percentage';
        $paytm->PAYTM_POST_DATA["discountValue"] = "2";
        $paytm->PAYTM_POST_DATA["invoiceAmt"] = '10';
        $paytm->PAYTM_POST_DATA["tax"] = 'SALES';
        $paytm->PAYTM_POST_DATA["description"] = '';
        $paytm->PAYTM_POST_DATA["callbackUrl"] = 'mysiteurl';
        $paytm->PAYTM_POST_DATA["checksumhash"] = $paytm->getChecksumFromArray($paytm->PAYTM_POST_DATA, PAYTM_MERCHANT_KEY); //Here checksum string will return by getChecksumFromArray() function.
        $responseParamList = $paytm->callAPI("https://pguat.paytm.com/PayTMSecured/app/restapi/sendsms", $paytm->PAYTM_POST_DATA);

        echo "<pre>";
        var_dump($responseParamList);
        die("test to die");

此代码给出了如下错误，

array(2) {
  ["errorCode"]=>
  string(9) "SMSINV-17"
  ["errorMsg"]=>
  string(18) "Json Parsing error"
}
test to die