require_once("PaytmChecksum.php");
              fwrite($log_file, PHP_EOL .'============= '.PHP_EOL.date('d-m-y H:i').' Paymnet recurring loaded ===  => '. PHP_EOL);

              /* initialize an array */
              $paytmParams = array();

              /* add parameters in Array */
              $paytmParams["MID"] = "Videom67952374755171";
              $paytmParams["ORDERID"] = $ORDER_ID;
              /**
              * import checksum generation utility
              * You can get this utility from https://developer.paytm.com/docs/checksum/
              */
                            
              $paytmParams = array();
              $mid = "Videom67952374755171";
              $orderId = $invoice_no;
              $merchant_key = "QTWh7PtoZoeONDaY";
              if($plan_type=='M')
              {
                $subscriptionFrequencyUnit = 'MONTH';
                $subscriptionExpiryDate = date('Y-m-d', strtotime('+5 months'));
              }
              if($plan_type=='Y')
              {
                $subscriptionFrequencyUnit = 'YEAR'; 
                $subscriptionExpiryDate = date('Y-m-d', strtotime('+5 years'));
              }
              $paytmParams["body"] = array(
                  "requestType"               => "NATIVE_SUBSCRIPTION",
                  "mid"                       => $mid,
                  "websiteName"               => "WEBSTAGING",
                  "orderId"                   => $orderId,
                  "callbackUrl"               => "https://merchant.com/callback",
                  "subscriptionAmountType"    => "FIX",
                  "subscriptionFrequency"     => "2",
                  "subscriptionFrequencyUnit" => $subscriptionFrequencyUnit,
                  "subscriptionExpiryDate"    => $subscriptionExpiryDate,
                  "subscriptionEnableRetry"   => "1",
                  "txnAmount"                 => array(
                      "value"                 => $order_amount,
                      "currency"              => "INR",
                  ),
                  "userInfo"                  => array(
                      "custId"                => $username_m,
                  ),

                  "subscriptionStartDate" => date("Y-m-d"),
                  "subscriptionGraceDays" => "2" 
              );

              fwrite($log_file, PHP_EOL .'============= '.PHP_EOL.date('d-m-y H:i').' Recurring payment request  paytmParams ===  => '. PHP_EOL); 
              fwrite($log_file, print_r($paytmParams, true)); 

              /*
              * Generate checksum by parameters we have in body
              * Find your Merchant Key in your Paytm Dashboard at https://dashboard.paytm.com/next/apikeys 
              */
              $checksum = PaytmChecksum::generateSignature(json_encode($paytmParams["body"], JSON_UNESCAPED_SLASHES), $merchant_key); 
              fwrite($log_file, PHP_EOL .'============= '.PHP_EOL.date('d-m-y H:i').' Recurring payment request  checksum ===  => '. PHP_EOL); 
              fwrite($log_file, print_r($checksum, true)); 

              $paytmParams["head"] = array(
                  "signature"               => $checksum
              );
              $post_data_rec = json_encode($paytmParams, JSON_UNESCAPED_SLASHES);
              /* for Staging */
              $url = "https://securegw-stage.paytm.in/subscription/create?mid=$mid&orderId=$orderId";
              /* for Production */
              // $url = "https://securegw.paytm.in/subscription/create?mid=YOUR_MID_HERE&orderId=ORDERID_98765";
              $ch_recurring = curl_init($url);
              curl_setopt($ch_recurring, CURLOPT_POST, 1);
              curl_setopt($ch_recurring, CURLOPT_POSTFIELDS, $post_data_rec);
              curl_setopt($ch_recurring, CURLOPT_RETURNTRANSFER, true); 
              curl_setopt($ch_recurring, CURLOPT_HTTPHEADER, array("Content-Type: application/json")); 
              $recurring_response = curl_exec($ch_recurring);