Himalayan bank API Integration php laravel html

Firstpage.php

<form method="post" action="secondpage.php">

<input type="text" id="amount" name="amount" value="" />

<select id="currencyCode" name="currencyCode">

<option value="524">NPR</option>

<option value="840">Dollar</option>

</select>

<textarea name="productDesc" id="productDesc"></textarea>

<input type="submit" id="submit" name="submit" value="Submit data" />

</form>

Secondpage.php

<?php

$var_value = $_POST['amount'];

$currencyCode = $_POST['currencyCode'];

$productdesc = $_POST['productDesc'];

$cost = $var_value *100;//product_cost//;// $ç = str_pad(rand(100000, 99999999999999999999),20,"0",STR_PAD_LEFT);

$randnum = rand(111111111,999999999);

$invoiceNo= str_pad($randnum,20,"0",STR_PAD_LEFT);

$amount = str_pad($cost,12,"0",STR_PAD_LEFT);

$merchantId = //your_merchant_id//;

$secretKey = //your_secret_key//;

$nonSecure = 'N';//nonce//;

$signatureString = $merchantId.$invoiceNo.$amount.$currencyCode.$nonSecure;

$signData = hash_hmac('SHA256', $signatureString, $secretKey, false);

$signData = strtoupper($signData);

?>

<form action="https://hblpgw.2c2p.com/HBLPGW/Payment/Payment/Payment" method="post" id="my-form">

<input type="hidden" id="paymentGatewayID" name="paymentGatewayID" value="<?php echo $merchantId?>"/>

<input type="hidden" id="invoiceNo" name="invoiceNo" value="<?php echo $invoiceNo ?>"/>

<input type="hidden" id="productDesc" name="productDesc" value="<?php echo $productdesc ?>"/>

<input type="hidden" id="amount" name="amount" value="<?php echo $amount ?>"/>

<input type="hidden" id="currencyCode" name="currencyCode" value="<?php echo $currencyCode ?>"/>

<input type="hidden" id="nonSecure" name="nonSecure" value="N"/>

<input type="hidden" id="hashValue" name="hashValue" value="<?php echo $signData ?>"/>

<input type="submit" id="submit" name="submit" value="Submit data"/>

</form>